Serenity, Nevada by Christina K
[Buffy the Vampire Slayer/Firefly]
Take the crew of Serenity and place them in modern-day rural Nevada (Mal gets to be sheriff!). Add some crazy vampires and an intinerant musician/Slayerette. Shake thoroughly, lean back and enjoy. Another awesome adventure from the fabulous Kiki!
When Hellmouths Collide by Kimberley Rector and LTLJ
[Buffy the Vampire Slayer/Hercules: The Legendary Journeys]
This ranks in my personal list as the most brilliant crossover of all time. The two mythologies are integrated seamlessly, logically and consistently with both universe's rules; the plot is twisty and complex, with both universe's villains represented; there's action, adventure, romance and humor; and every single character is written with dead-on accuracy and affection, the dialogue truly perfect. Go. Read. Now. You can thank me later (and you will).
Runaway Trains at 3 a.m. by Christina K
[Buffy the Vampire Slayer/Smallville]
Pop Quiz Question of the Day: If a supernatural teenager from Sunnydale, California heads east at 70 mph, while a super-powered teenager from Smallville, Kansas is heading west at 65 mph, at what time will they meet up in a Greyhound bus station in Denver? Just in time for some lovely interaction between two unlikely people, a couple of great cameos, and one of the most solidly characterized crossovers you'll ever find. It's not like I'm objective about Kiki's writing, but everyone else in the universe has recced this one, so I feel confident in my own. Don't miss the sequel, Lines of Communication.
Sailor's Delight by General Jinjur
[Buffy the Vampire Slayer/Stargate Atlantis]
A post-apocalyptic crossover, serious and sober and chillingly atmospheric. Dawn wakes to find the world has ended; as she heads alone for California, she stumbles across Jeannie McKay Miller. It totally works.
Bridges by Tassos
[Buffy the Vampire Slayer/Stargate SG-1]
After the collapse of Sunnydale, Jack O'Neill receives a call about a will -- and a son he never knew he had. Meanwhile, Xander Harris is trying to babysit a herd of Slayers in Cleveland, when a man shows up on his doorstep.... Two of the most overused cliches in fanfic collide: Xander's Real Father and the dreaded Stargate/Buffy crossover. But surprise, surprise, this one's really good! The characterization on Jack and Xander is dead-on perfect, with everyone else running around nicely dilineated. KikiRec
Donna the Vampire Slayer by Nomad
[Buffy the Vampire Slayer/The West Wing]
I keep running into crossovers that make me spit with jealousy for not being able to do that, and Nomad's Donna the Vampire Slayer is one. Just accept that there are vampires in Washington DC (which shouldn't come as news to anyone who watches CSPAN), and let the story carry you from there. Nomad uses a fine balance of absurd humor and occasional near-total seriousness, coupled with dead-on characterization and dialogue -- if the Senior Staff found out vampires were real, this is how they would react. And don't get me started on what happens to Sam in the sequel...
The Roommate of +10 Confusion by Grevling
[Calvin & Hobbes/Foxtrot]
"There must be some scientifically sound way for Jason Fox to be able to quantify his new college roommate, but he hasn't found one yet that fits. Especially when he factors in the stuffed tiger." A really fascinating crossover, very nicely pulled off. Yuletide 2010
Wizards in Winter by vibishan
[Calvin & Hobbes/Young Wizards]
"The advertisement is a spiky red impact bubble on the back of his box of Chocolate Frosted Sugar Bombs. Mail in just five box tops for your very own HOW TO BE A WIZARD KIT* ." Calvin is perfect. KikiRec
Persistent Illusions by jedibuttercup
[Castle/The Sorceror's Apprentice]
Because you know if Beckett and Castle investigated the dead bodies in Drake's apartment, they would SO not let it all go.
Ankh-Morpork, Avenged by HonorH
[Discworld/Avengers]
Loki invades Ankh-Morpork. Big mistake. But a very, very funny one.
The Dalek Invasion of Discworld by TigerKat
[Discworld/Doctor Who]
The Daleks invade the Discworld. Also a big mistake. Also funny.
Companionship by akamarykate
[Doctor Who/Early Edition]
Set during the Year That Wasn't. Lovely focus on one area of the world, and Gary and the newspaper (and Cat!) are worked in very well.
Wibbly-Wobbly Timey-Wimey Invisibling Thing, or Four Times Jack Carter Met The Doctor And One Time He Didn't by galaxysoup
[Doctor Who/Eureka]
"Eureka is a town full of geniuses. Naturally, the Doctor must poke it with a stick." Completely perfect crossover starring Jack Carter and multiple incarnations of the Doctor. Side-splittingly giggly fun (except for that one part, but that's different...) KikiRec
The Man With No Name by FrostFyre7
[Doctor Who/Firefly]
River senses a storm coming, but it's nothing she or Serenity's crew could have predicted. And the Doctor wanders after losing Rose, searching for a way to stop the pain... A truly brilliant crossover; both River and Ten will break your heart.
All in a Day's Work by miss_baxter
[Doctor Who/Hitchiker's Guide to the Galaxy]
Donna Noble has to save the world from the Vogons. Screamingly funny fusion of the two universes, told with a dead-pan HGttG voice.
Relatives and Relativity by Emeraldwoman
[Doctor Who/Sense & Sensibility]
Nine, immediately post-regeneration, and two sisters remind him what he still has to live for. Beautifully done, but what else do you expect of Yahtzee?
Preludes by seren_ccd*
[Doctor Who/Sherlock (BBC)]
LeStrade hides on a back porch during a bachelor party, and makes a new friend in Amy Pond. Absolutely adorable (and explains a few things in canon).
Odds Are (We're Gonna Be Alright) by lady_ragnell
[Elementary/Marvel Cinematic Universe]
"Sherlock knows that had Project Insight worked as HYDRA intended, he and Joan would both be dead. The knowledge does not sit well with him." Clever and believable.
Wish You Were Here by Tassos
[Haven/Criminal Minds]
"When the FBI's BAU follow a serial killer to Haven, Maine, they find that murder and mystery are a lot more complicated in the unassuming sea-side town. The local cops don't want them there, the crime scenes don't make sense, and it doesn't take long for them to get in over their heads." I read this is with minimal knowledge of Criminal Minds, and still totally loved it.
Home Is Where Your Story Begins by FaithDaria
[Joan of Arcadia/Supernatural (passing reference to the Dresden Files)]
God told Joan, "I said your life will be easier. Easier doesn't mean better." This totally shouldn't work as well as it does, but it totally, totally does. A chance encounter on Joan's journey twines her life forever with the Winchesters'. Really extraordinary. KikiRec
Nerds of the Earth, take note! by emeraldwoman and brownbetty
[Leverage/Iron Man]
Two great tastes that taste great together! Hardison is "recruited" by SHIELD to clean up a... small problem, and Tony shows up to "help". Eventually, so does the team. I'm obviously a sucker for great Hardison POV, and the authors also capture Tony and SHIELD crew brilliantly.
The Princess Bride Job by themonkeytwin
[Leverage/The Princess Bride]
No, no, I'm serious. It's cracked out, but logical in its own way, the twists and turns of the movie adjusted to match, well, the way things would have gone if Westley had come to the Leverage team for help retrieving Buttercup from Vinzini. There are a few points where I seriously almost died laughing ("Mawwiage..."), and the voices are scarily perfect throughout. Read This Now.
Second Mouse by AlphaFlyer
[Marvel Cinematic Universe/James Bond]
"When HYDRA is suspected to be carrying out illicit activities in Scotland, SHIELD and MI-6 are asked to cooperate. Two covert agencies on the same turf -- Barton & Bond, Fury & M, Coulson & Moneypenny -- what could possibly go wrong? (Oh, and who exactly does the gorgeous redhead work for?)" Crazy good crossover, set pre-Avengers.
Locust Wind by AlphaFlyer
[Marvel Cinematic Universe/James Bond]
"Following the traumatic events of the Convergence over Greenwich, it's becoming clear that not everything that came out of the rift went back in -- and somebody is seizing the opportunity. Once again, MI-6's and SHIELD's top agents, now with the addition of the Black Widow, find themselves thrown together, facing ... what, exactly?" A worthy sequel to Second Mouse, and a neat interstitial between Thor 2 and Winter Soldier. Clint/Natasha in passing.
Assets Out of Containment by follow_the_sun
[Marvel Cinematic Universe/Jurassic World ]
"After CA:TWS, Bucky Barnes suspects HYDRA is running a project in a little place called Jurassic World, and decides to go poke it with a stick." Crossover woven in and around Jurassic World; Bucky is sarcastic and funny, and the guest stars are excellent.
Go-Cart Charlie by Red Soprano
[Medium/NUMB3RS]
A nifty crossover, as Allison's family vacation to Disneyland gets derailed by a persistant ghost, trying to save her son's life. Charlie isn't what Allison expects to find, but the ensuing relationship between the two families as they track down a saboteur is fun and touching. If you've seen either show, give it a shot.
Volatile Compounds by gekizetsu
[NCIS/Supernatural]
A difficult crossover played absolutely straight, making it even harder to pull off. Nicely balanced, with both teams playing a strong role, and it works on every possible level.
When Worlds Collide by
[NCIS/Supernatural]
"When a kidnapped Tony DiNozzo is rescued by legendary - and supposedly dead - serial killers Dean and Sam Winchester, the NCIS team takes over the Winchester investigation. What they find is a file filled with contradictions and impossibilities." Tony and Dean are particularly perfect, but the whole thing is a brilliant crossover epic. You only need basic familiarity with each show. KikiRec
Take a Long Line by Derry
[NUMB3RS/Supernatural]
Don Eppes arrests Dean Winchester, but there's a lot more to the story. The universe integration works by not trying too hard; Charlie's math does some of the thinking that you've always wanted the FBI guys on Supernatural to do, and everyone's voices are spot on.
Crooked Paths by themonkeycabal
[Stargate Atlantis/Farscape]
themonkeycabal simply has one of the deftest crossover touches I've run across. This one pits Rodney McKay against the Uncharted Territories and his old college rival -- John Crichton. John, Rodney and Aeryn are all beautifully voiced, the Farscape universe is lovingly portrayed, and the interactions are just wonderful.
Displacement (or The Longest Three-Week Day) by Michelel72
[Stargate Atlantis/Doctor Who]
Temping at a conference in Oxford, Donna Noble helps Rodney McKay save the world -- and then things really get interesting. Donna/Rodney is possibly the Most Awesome Crossover Pairing Ever and it totally works here.
The Merry-Go-Round Broke Down by Merlin Missy
[Who Framed Roger Rabbit/Miscellaneous]
This is sick, twisted and utterly brilliant. Words cannot express.... Jessica Rabbit is accused of the murder of 'digi' Lara Croft, and Roger, with the help of young Freddie Valiant, swings into action to clear her name and catch the killer. A fabulous update of the movie, incorporating modern characters and animation and twisting it all together. (References to all kinds of adult material, but seriously, they go by so fast you'll just snicker, throw popcorn and move on.)
Ekphugion by Shaye
[Vorkosigan/Battlestar Galactica]
The Galactica has finally found another world of humans -- warlike humans with itchy trigger fingers, but humans nonetheless. Now the Viceroy and Vicereine of Sergyar have to figure out what to do with them. Marvelous. 2005 Multiverse Ficathon.
I'm not a sucker so I don't need a bodyguard by musesfool
[Angel/Batman:TAS]
"Cordelia never expected to get a second (or possibly third) chance after she got to say goodbye to Angel, but with the hellmouth opening in Los Angeles and the walls between dimensions coming undone, she finds herself in Gotham." One of those crossovers you don't see coming, then can't imagine why not. Cordelia's interaction with Bruce is classic.
Mattaltu by LithiumDoll
[Angel/Leverage]
Many have tried, but few have succeeded this well at crossing over Leverage and Angel. A solid plot with great dialogue and a killer of a last line.
Days Like This by killa
[Angel/Supernatural]
Dean and Angel in a tunnel, fighting a demon. It goes about as well as you'd think. A thoughtful, well-executed crossover.
To Conquer Fear by Mara Greengrass
[Batman/CSI]
Gil Grissom and Batman (Forensics Geeks R Us) defend Las Vegas from the Scarecrow with the help of, um, everyone. Written largely in email form, and nicely done.
Betty and the Bat by wrigleyfield
[Batman Begins/Ugly Betty]
Seriously, I'm not making this up. At the end of Season 1, Betty goes to work for Bruce Wayne as his personal assistant. And it works out just exactly as awesomely and adorably as you'd think. Bruce would be so much better off with more people telling him not to talk about himself in the schitzophrenic third person....
The FOP Job by Mara G
[Batman Begins/Leverage]
Two cops walk into bar.... A completely awesome conversation between Jim Gordon and DC Bonanno re: dealing with highly effective vigilantes and how to cope.
The Father Goose Tales by litmouse
[Buffy the Vampire Slayer/Various]
I should not, in good conscience, recommend this series. I want too badly to beat the author about the head with periods and semi-colons until he learns to use them properly -- or, at all. However, once I got past that (and it took surprisingly little time), this series entertained the hell out of me. Long Xander/Faith-centric crossovers with L&O:SVU, Alias and Stargate SG-1 (plus a few oddballs like Gilmore Girls, no, I'm not kidding) work ridiculously logically and with really wonderful characterization (including an adorable gang of OC Slayers and some Watchers) and dialogue. Also, there's Weiss-ness, which is always going to suck me in. The SG-1 story isn't finished yet, but there's a lot to read before you hit that point. Give it a try.
Harry Potter and the Key of Dagon by Don Sample
[Buffy the Vampire Slayer/Harry Potter]
Okay, this is not great art. It's quite indulgent, a little light on plot, and generally fluffy. But it's also one of the more intelligent Buffy/HP crossovers I've run across and the author intended it that way, so, major points. The universes are integrated with a fair amount of thought and all of the characters sound like themselves; you're going to get a lot of rehashing of Buffy and HP plots, but they're integrated well into dialogue and storytelling. And it's fun. Instead of angsting all over the place, people are happy and getting along and enjoying themselves (mostly), which is reason enough to read this, even if you think Dawn taking Draco's wand away from him and wearing it in her hair for a week isn't. (I think it totally is, but that could just be me.) Some shippiness, but only one pairing gets any focus (and no, I'm not telling you which one it is, except that it's het). Give it a shot.
Slayer by Scribe
[Buffy the Vampire Slayer/The Magnificent Seven]
Spike runs afoul of a time-altering demon, and has to go back in time to save one of Buffy's ancestors before he can be killed. Which of the Seven is it? The prose needs a little polishing, but the dialogue and characterization are good, and the situation bounces between scary and hilarious.
The Date Series by LastScorpion
[Buffy the Vampire Slayer/Smallville]
In a nice little alternate universe, Dawn and Clark wind up at college together, and somehow talk Lex and Buffy into a Double Date. The series takes off from there, expanding a short one-shot into two longer, plottier sequels building the relationships between all four characters with excellent characterization and a real love for both universes. It's not deep and makes no pretense of being so, but it is well-done and absorbing. Even better, she AUs herself with World of Perpetual Wednesday, World Without Superman, in which two entirely different Lex Luthors find themselves with another dimension's Dawn Summers in the Sunnydale of a fourth universe altogether. Getting there wasn't exactly what any of them had in mind, and getting back home is only half the fun.
The Scarab by BK the Irregular
[Buffy the Vampire Slayer/Stargate SG-1]
Using the remains of the Initiative and Riley himself, Bruce not crosses over the two universes with a tight, twisty plot, excellent characterization, dialogue that is dead-true to both shows, and a sense of humor about the whole thing that never quits.
Dear Frankie by offbalance
[Buffy the Vampire Slayer/Supernatural]
A wistful AU for Faith. KikiRec
Smoke on the Water by ratherastory
[Burn Notice/Supernatural]
"Former spy Michael Westen has enough problems of his own not least of which is figuring out who burned him and why. Now, on top of that, his mother is accepting jobs on his behalf. He really doesn't have time for this, but when he starts investigating the unsolved deaths of young people in Miami, he finds himself crossing paths with an unlikely pair of brothers." Fiona is woefully underused, making this very much a "Boy's Day Out", but Michael's POV is dead-on (and makes it easier for non-SPN fen to get into the story). KikiRec
How Are the Mighty Fallen: An Instruction Manual by Roga
[Discworld/Heroes]
"There were two big differences, Matt felt, between Ankh Morpork and New York City." A wonderfully silly crossover. KikiRec
Proving a Negative by Zeborah
[Doctor Who/White Collar]
Amy and Rory hit an art exhibition on the way to Utah -- and get arrested for being art thieves. But Neal knows something else is going on here.... Very funny.
Hello, Major Tom by themonkeycabal
[Doctor Who/Farscape]
We should all get holiday presents like this, because watching Crichton have a close encounter with the TARDIS Trio? Priceless. Jack's reaction to meeting his all-too-human hero is lovely, and watching Crichton and the Doctor snark at each other is a hell of a lot of fun.
Past Improbable by sixth_light
[Doctor Who/Torchwood/Bones]
The situation is wildly improbable, of course, but everyone treats it so seriously that you have to as well -- when you're not giggling hysterically at the crackling dialogue snapping back and forth between all the characters. sixth_light somehow combines the running plot arcs of Brennan's past with Jack Harkness's, and then the TARDIS shows up to reunite with Jack and join the fun. The universes are integrated quasi-logically, you get enough backstory to keep up even if you don't know one of the shows. (I link to Part 13; the first 12 parts are linked at the top.)
I Was Only Borrowing Time (I Was Going to Give It Back) by Sam the Storyteller
[Doctor Who/White Collar]
Neal's friendship with the Doctor, not actually in linear order. Very well-done and remarkably true to all characters concerned.
Journey's Dawn by ameretrifle
[Doctor Who/Young Wizards]
Donna Noble is missing a part of herself -- but the Powers That Be have an offer for her.... Not for the pro-Ten crowd, but very well done. Linking to Part 10; all other parts linked to at the top. KikiRec
Noticing by niftywithanN
[Dresden Files/Batman]
"In which Gentleman John Marcone is bored, a disturbance at a Chicago charity ball catches the attention of a certain Dark Knight, and Harry Dresden is late." KikiRec
Time Bomb by Christina K
[Dresden Files (books)/Firefly]
A strange girl named River appears in the middle of Chicago, and Harry gets assigned as her babysitter. Then a Faerie queen gets involved, and Harry's day kind of goes downhill from there. A fun ride with great integration of the universes -- both River and Harry are perfect.
Persistant Mysteries by Shaye
[Farscape/Firefly]
When Serenity's crew stumbles onto an ancient cryochamber in an ancient bunker, they don't expect to find someone alive inside of it -- or for that someone to be a Nebari thief so very far from home. Shaye's Chiana and River are amazing, and everyone else shines as well.
Prompt the Second by Tassoss
[Farscape/Stargate SG-1]
Cam Mitchell is trapped far away from his team, with a man who looks like him, but very much isn't.
A Million Light Years From Home by Victoria P.
[Firefly/Harry Potter]
Kaylee brings a big black dog back to the ship, but he's much more than he seems -- a wizard far from home. Post-Serenity and Order of the Phoenix, an unlikely crossover blended together just beautifully. Serenity's crew seen through Sirius' eyes is a wonderful thing.
Change Is the Only Constant by Mara Greengrass
[House/Batman]
When Bruce Wayne becomes Dr. Gregory House's latest patient, House's hidden past might just be disclosed... Both of the universes are somehow integrated, House's voice is dead-on, and the DC cast plays exactly as they should. So very beyond cool.
Hallowed Be Thy Greg by Suzvoy
[House/Joan of Arcadia]
It's just a short, inoffensive little crossover -- that will leave you on the floor rolling around and dying of laughter. Suz nails both of her characters and the result is snarkily hilarious.
Five times the Leverage Crew was not in Gotham, no, really, they weren't, no. by noelia-g
[Leverage/Batman]
What it says on the package. < snicker > KikiRec
The Five-0 Job by Tassoss
[Leverage/Hawaii Five-0]
Another fun tassoss crossover. Do not try to make the plot make sense, because it doesn't (which is fine, because H50 plots almost never make sense), but enjoy Danny being driven absolutely nuts by events out of his control and a bunch of thieves telling him to relax. :)
The Crossover Job by scrunchy
[Leverage/Sherlock (BBC)]
I hate Sherlock, but I love this story, because Inspector Lestrade really is this awesome. Anyway, he has a past with Sophie and she turns up and... well, it's just excellent. KikiRec
Exotic Particles by facetofcathy
[Leverage/Stargate: Atlantis]
Two random particles meet in an airport. KikiRec
Wargames Didn't Play Out Like This by aurora-novarum
[Leverage/Stargate SG-1]
In his larcenous past, Hardison has a close encounter with Area 52.
I Lie, I Cheat, I Steal (and I Just Don't Get Any Respect) by fiercelydreamed
[Leverage/White Collar]
The Leverage team makes Neal an offer he can't refuse. Obviously, things go completely off the rails fairly quickly. Categorize this as gen-ish; references are made to several pairings, but it was hilarious enough that I don't care too much (and I'm sort of mildly in favor of both of the multis, so there you go). Funny and fabulously in character, and Hardison's POV is the best.
A Watcher's Duty by jedibuttercup
[Live Free or Die Hard/Buffy the Vampire Slayer]
What life would be like if Lucy McClane was a Slayer. I am ded from squee.
Five Muppets Isaac's Pretty Sure He Never Hired by Amy (fox1013)
[The Muppet Show/Sports Night]
CrackFic! Oh my god! Hilarious, startlingly in-character, screamingly funny crackfic! Amy takes it just seriously enough to make it all the more howlingly funny. Example: "Dan's face fell. 'She's just- she's a really neat pig, is all. And you'll hurt her.'" Continue from there. Trust me.
What Kind of Day Has It Been? by Victoria P (aka musesfool)
[The Muppet Show/Supernatural]
This encompasses a level of crazy that frankly impresses even me. And it's hilarious, too. :)
The Trouble With Harry by azarsuerte
[NCIS/Doctor Who (old and new)]
When Admiral Harry Sullivan goes missing on US soil, NCIS is called in to investigate, and Abby gets quite the blast from her past. A nearly flawless crossover with dynamite voices. (Evidently part of a series, but it stands on its own.)
Agent Afloat: Atlantis by Mhalachai
[NCIS/Stargate Atlantis]
In a novella-length AU season 6, Ziva gets a new assignment far from home, but her worlds still persist in colliding. Really fascinating universe integration with gorgeous Ziva POV; the writing is strong and almost poetic in places. Tony/Ziva at times, references to McShep and Ziva/Jenny -- I found them easy to blow past. KikiRec
Highly Classified and Very Hush-Hush by rageprufrock
[NCIS/Stargate Atlantis]
Naked Marines appearing out of thin air do not make Gibbs a happy man. Particularly when their base commander is an Air Force colonel, and none of this makes any sense. I believe I speak for much of fandom when I say, "Thank god, now I don't have to write this."
NCIS and the Haunted Computer by Tassos
[NCIS/Supernatural]
Short and somewhat fluffy, but told in a hilarious deadpan. There's an equally amusing sequel.
Parrot by penknife
[Pirates of the Caribbean/Harry Potter]
Jack Sparrow at Hogwarts. You may begin being terrified now. (Also read Pieces of Eight for some (non-crossover) post-AWE snapshots.)
The Involuntary Expansion of the Mind by Jade Eclipse
[Psych/Angel]
Shawn finds out the downside to really being psychic. Almost entirely the Psych crew, with cameos from Angel and Cordelia.
Hop, Skip and a Jump by Nestra
[Stargate Atlantis/Doctor Who]
If your team was trapped on a Wraith ship, would you want to run into The Doctor and Martha? Yeah, I'm not sure, either. But it'd be interesting :)
Drink Up, Look at the Stars by Kuwdora
[Stargate Atlantis/Farscape]
A way-cool meeting between John Crichton and John Sheppard during the former's visit to Earth. Sheppard's POV on Crichton is really nicely done, and seeing Moya, Pilot and the others through his eyes is a real treat. 2005 Multiverse Ficathon. KikiRec
The Big Bang and Everything After by cgb
[Stargate Atlantis/Firefly]
It's one of those pairings you find it impossible to believe will work until someone pulls it off, but this is, in fact, McKay/River. cgb does a lovely job with River's POV, and McKay is touching as a man pulled out of his own time. 2005 Multiverse Ficathon. KikiRec (I had this wrongly attributed for the longest time, and I deeply apologize.)
Interpreted Languages by Parrotfic
[Stargate Atlantis/Heroes]
"When Micah first started talking to machines, they didn't talk back." Very short, very cool.
Clarke's Law by Isis
[Stargate Atlantis/Harry Potter]
Carson Beckett makes a discovery tying back to his school days that might be the key to defeating the Wraith. However, since the school in question was Hogwarts, this might not be as simple as it sounds. Isis does a wonderful job of integrating the rules of the two universes, both in the plot and through the characterization.
Classified by Dira Sudis
[Stargate Atlantis/NUMB3RS]
Dira attempted one of those crossovers you never think could work and pulled it off in gorgeous style by simply not forcing it too hard. The circumstances make perfect sense, the characterization is achingly on-target, and Don's POV is beautiful. Very real in ways you wouldn't expect going in, and just awesome.
The Roads of the World by celli
[Stargate Atlantis/Supernatural]
Another of those weird little crossovers that works well not by not pushing it too hard. Celli's Dean is perfect; a little lost and a little broken, but finding someplace where he fits.
No Respect for Normal Dimensions by Caladria
[Stargate SG-1/Discworld]
In which SG-1 meets the Luggage. And DEATH.
Tempus Fugit by Anonymous
[Stargate SG-1/Doctor Who]
"Scientific accuracy meets 'wibbly-wobbly timey-wimey stuff'." Sam Carter meets the Doctor.
Pathways by Tassos
[Stargate SG-1/Farscape]
Tassos has a really deft hand with crossovers, and this is another good one; she integrates the wormholes of the two universes in a way that not only makes perfect sense, but builds a great framework for her story. The characters are integrated equally nicely; it's a fun romp and an impressive achievement.
Actualize This! by Helena Handbasket
[Stargate SG-1/Sentinal/Invisible Man]
I was force-fed three episodes of Sentinal, and felt no desire to return. I'm not happy about Daniel coming back to Stargate. And I could not figure out how Darien and Bobby could interact with any of the above. So it was with great skepticism that I entered into this crossover. Within three paragraphs, I was laughing like a loon. The dialogue is too funny for words, and the takes that all six of these men have on each other are snarky and perceptive and truly hilarious. Forced by various commanding officers to attend a "partnership-building" seminar in Canada, they stumble (of course) into a Secret Plan, which they must proceed to thwart in their own inimitable ways. Even if you've only seen one or two of the shows, don't let that stop you -- this is priceless stuff. And it's not slash!
Migratory Birds by nekare
[Supernatural/X-Men (movie)]
Pre- and post-end of the world; mutant brothers wind up on opposite sides of a war.
Marks and Scars by E. H. Smith
[Vorkosigan/Harry Potter]
Professor Snape makes one little wish -- "Show me one man more wretched than I." -- and finds himself with an unexpected visitor in the form of Mark Vorkosigan. Saying the pair of them bond doesn't quite cover it... The story continues in Without Enchantment and No Great Magic.
Time Shall Not Mend by A.J. Hall
[Vorkosigan/Harry Potter]
Ekaterin Vorkosigan wishes to be anywhere but here, and finds herself coming to the aid of two young wizards on a planet long ago and far away. Then Draco Malfoy returns the favor. The summary doesn't do it justice, because nothing could; just accept that A.J.'s gift for making Draco likeable without fundamentally changing him really comes through. One or two quibbles on one or two characters; the rest are well done (I adore his Ivan).