Crossovers: Authors A-I

Wargames Didn't Play Out Like This by aurora_novarum  (Leverage/Stargate: SG1) - Hardison has an unusual run-in with "the Man".
Ficlet by fleshflutter  (Labyrinth/Supernatural) - Crack!
Take the sky by irnan  (Firefly/Supernatural) - Dean and Sam would fit right in with the crew of Serenity. Right?
Sour Cherry Pie Life by faithburke  (Supernatural/Criminal Minds) - Dean has retired to the civilian life. Too bad no one told the serial killer currently stalking teenagers in Indiana.
The Righteous Man in the Shallow Grave by bellatemple  (Supernatural/Bones) - When an unidentified body is found in an illegal grave in a field in Pontiac, Illinois, the body gets shipped to the Medico-Legal Lab at the Jeffersonian for identification, and Death calls Tessa in with a warning: "The righteous man has broken, and the angels have breached Hell's gates."
Earnest by daroos  (Numb3rs/Supernatural) - The boys run in to Charlie on a Chupacabra hunt.
Kissing Lessons by dotfic  (Supernatural/Some Kind of Wonderful) - Watts lied to Keith about how she learned how to kiss.
Dirty Jobs, The Winchester Edition by frostian  (Supernatural/Dirty Jobs) - Mike Rowe and his crew drop by the picturesque New England town of Derry to film an episode of Dirty Jobs only to find they've become human sacrifices. Then, they're rescued by two psychos armed and ready to rock-n-roll with monsters thought to be the creations of drunken men who had nothing better to do than tell tall tales. And people think reality show industry is scripted.
This Bitter Earth by art_savage  (Supernatural/Criminal Minds) - The Winchesters and the FBI's Behavioral Analysis Unit investigate the same case, a series of mysterious deaths on the grounds of a South Carolina plantation.
(Fear) The Reaper by baylorsr  (Supernatural/Psych) - Henry bent over and pointed his finger in Shawn’s face. “Zombies,” he told his son sternly, “are not just for fun. You either take them seriously, or you end up one of them.”
The Exiles by briarwood  (Supernatural/Angel) - Two years ago, Kate Lockley was kicked out of LAPD because of her obsession with the things out there in the dark. Now she’s a deputy in a small California town and something she knows isn’t human has abducted a young woman. Kate tracks the thing to its lair but she’s not the only one hunting it. When she runs into John and Dean Winchester, she comes to realize that despite her experience fighting vampires, demons and zombies, she ain’t seen nothing yet.
Where Monsters Fear to Roam by caffienekitty  (Monsters Inc./Supernatural) - There are some closets that scare the monsters.
In The Shadows Lurk by donutville  (NCIS/Supernatural) - Peoria Police Officer Tony DiNozzo winds up in hot water when he finds himself entangled with both a serial killer and a mysterious man in a black Impala.
Unexplained (Sequel: Explained) by ALEO (Numb3rs/Supernatural) - Thirteen grisly murders. When Don stumbles on the scene of the final murder he fears he is about to become the fourteenth victim.
Devil's Gateway by abendstern1601  (Supernatural/Dark Angel) - Staring at the brothers, down at the calendar in his hand and back again, Alec had the hysterical thought that, even if he did get himself into trouble a lot, no one could accuse him of not being creative about it.
Exotic Particles by facetofcathy  (Leverage/Stargate: Atlantis) - A woman named Parker meets a man in a coffee shop. I trust you'll recognize him.
Take a Long Line by derry667  (Supernatural/Numb3rs) - Crossover with Numb3rs. The Eppes brothers encounter the Winchesters.

Harry Potter

The BeggarThief by gravidy - Hermione Granger has enough problems without worrying about Pureblood kidnappings and techno-geeks. The last thing she needs is Draco Malfoy breathing down her neck.
Queen of Heaven by riptey - Draco's only friend in prison is a spider, and its venom causes hallucinations of Hermione. The only problem is that Dream Hermione keeps insisting she's real.
Those Kinds of Things by AKA Jay - Draco cheers Hermione up, which was almost exactly the opposite of what he was trying to do. Contains Draco-baiting, thoughts of violence, and Hermione very carefully not noticing things about Draco.
Blood-Ties by beren_writes - Draco has a mission from Voldemort to finally kill The Boy Who Lived. He has been subject to Voldemort's ministrations to make sure he does not fail, but nothing is ever certain when Harry Potter is involved.
Macbeth by cyropi ‘Come what come may, time and the hour runs through the roughest day.’ Voldemort’s second rise to power and a part in Shakespeare’s infamous Scottish Play make this fitting for Hermione – especially when she discovers a darker side to Draco Malfoy. PreHBP

Supernatural: Pre-series

The Long Narrow Rope by pdragon76 - It’s been said that roots and wings are the only two lasting bequests you can give your kids, but sometimes all you’ve got is guns and how to use ‘em.
The Hapless Soldier's Sigh by bad_peppermint - In the summer of '88, a man called Frederic Lance summons John Winchester to Montana to find out who or what is killing off a small town's children. Burdened with a demanding five-year-old, a reclusive nine-year-old, and an employer who doesn’t hide his issues with John’s parenting methods, John could do without a case that has no leads, no M.O., and no clues except for a whole lot of field mice and some body parts. And what kind of monster is this interested in teeth?
Weekend with the Winchesters by innocentculprit - Sometimes John thinks hunting would be a more peaceful option.
Tioga Road by greeneyes_fan - You can't put honey back in the comb, and you can't turn a soldier back into a child. Case-fic, 1997.
The Night Dean Winchester Ruined His Date’s Prom (But Got Laid Anyway), or How Lyla Durand Learned to Stop Worrying and Love the Bad Boys  by Like-A-Raven-14 - It never goes well when the Winchesters attempt the "normal" things in life...
The Tao of Dean by Kerry - The way of Dean Winchester.
Open Season by chemm80 - Dean and Sam experience small town life, for better and worse.
Unexpected Company by dotfic - The one where John has wings, Sam is a toddler, Dean is seven, and Bobby is in way over his head.
Trost Und Freude by gwendolyngrace - Saginaw, Michigan, 1990: Going holiday shopping may hold more hazards than just the insane crowds and parents hell-bent on the buying the latest toy. John goes undercover to look into a series of accidents at the local mall. Meanwhile, Dean and Sam respond to Christmas-season festivities at school with unexpected results.
It's A Cold Hand That You Feel by i_speak_tongue - Tonight, Dean cares too much about Dad to let him do something this dumb. Tonight, there will be mutiny.
Four Times the Winchesters Had to Move (And Once They Didn't) by dodger_winslow - Four times the Winchesters had to move (and once they didn't).
The Square Root of Pi by x_strangeangels - Dean hated Poughkeepsie but at least he wasn't the one starting high school there.
The Taming of the You-Know-Who by innie_darling - Minor AU. Dean talks John into staying put for all of Sam's freshman year of high school, and Sam is thrilled that he can make friends and have them over, that he can act like any other kid his age. But when Sam develops a crush on a girl, John lays down the law - Sam can't have a girlfriend until Dean settles down with just one girl too - and that means Sam won't rest until he's come up with the perfect plot.
Seven by july_july_july - "All right, Dean," John spoke to the apparently empty house. "You've left me no choice. I'm going to have to go room to room."
Ten Going on Thirteen by dodger_winslow - When John is wounded, his life is in Dean's hands.
Freaks and Monsters by dodger_winslow - Dean's friend's in trouble, and he doesn't know how to help.

Crossovers: Authors J-R

And Today We Have Naming of Parts by medjai_trowa  (Supernatural/Leverage) - How Eliot Spencer became Eliot Spencer.
Pirate!Dean series by the_mad_fangirl  (Pirates of the Caribbean/Supernatural/Transformers 2007) - Sam discovers a way to buy Dean time.
Bedtime Story by the_mad_fangirl  (Labyrinth/Pirates of the Caribbean) - Jack babysits.
January Girl by parenthetical  (Supernatural/Harry Potter) - With Sam trying out normal life at Stanford and his father working an undercover gig across the country, Dean is on his own and getting reckless. While investigating a series of mysterious deaths, he runs into a strange witch called Luna Lovegood, who is searching for what she calls a 'Horcrux'. (Seriously?) Suddenly Dean finds himself dealing with evil wizards, broomsticks, Bat-Bogey Hexes, Dementors, mirrors which order him to wear a pointy hat, and much more - all the while trying not to think too much about Luna's last name and whether it's accurate.
A Friend In Need by pandarus  (Good Omens/Supernatural) - Aziraphale is visited by an acquaintance in need of assistance.
When Summoning, Please Watch The Wording by Ryuuza Kochou (Supernatural/Good Omens) - Dean and Sam fall into the hands of Satanists, who, naturally, want to use Sam as the vessel for the Golden Eyed Demon. Well...they do get A Certain Golden Eyed Demon. And an avenging Angel. And a serious posterior whooping.
Run Away You Want It by listentothemath. (Veronica Mars/Supernatural) - Like recognizes like and old dogs don’t learn new tricks. Read: she smells a mystery.
The Good Fight by Nancy T. (Numb3rs/Supernatural) - The Eppes and Winchester brothers team to help a student of Charlie's, the victim of a horrific crime. Supernatural content, but Don & Charlie aren't going to go all ghostbusters on you.
Once Upon a Time in the West by marinarusalka  (Supernatural/Terminator movies) - The Winchesters and the Connors happen to do their shopping in the same place. Smut ensues. Shameless PWP.
Encounters with the Enemy by legoline  (Supernatural/NCIS) - They really thought they were done with being arrested at crime scenes.
Dust in the Wind by lyra_wing  (Supernatural/American Gods) - Future fic. Erm. Hard to explain. This is a crossover with American Gods, but you don't need to read that to understand what's going on.
Today's Tom Sawyer Series by ladyjanelly  (Supernatural/Dark Angel) - Sam finds Ben after his escape from Manticore.
On the Run Driving In the Sun by liptonrm_fic  (Supernatural/The O.C.) - Sandy Cohen has a new client. (I don't watch The O.C., but I had no trouble following this story and caring about the characters.)
Deja Vu by redrikki  (Homicide/Supernatural) - In the summer of 1993, someone is killing young women on the streets of Baltimore and John Winchester is the main suspect.
Defect by kikkimax  (Supernatural/Criminal Minds) - The FBI captures Dean shortly before his deal with the demon comes due.
Be Kind to Your Shadow by pervyficgirl (Batman/Buffy) - Jason gets into a bar fight in Cleveland.
Stargate SG-1 Crossover by lyndseas (Batman/Stargate SG-1) - There's a flash and Tim is...elsewhere.
Thicker Water by pprfaith - Arthur and Natasha rarely make it to their Gamma's birthday, but business keeps them in touch.

Crossovers: Authors S-Z

Crossed Paths by Vanessa Sgroi (Supernatural/NCIS) - On a wintery night, Sam and Dean Winchester by sheer happenstance cross paths with two stranded Special Agents from NCIS. Much to the brothers' surprise, they discover they actually have some things in common.
Faith Like a Stone, Sinking Fast by skieswideopen  (Criminal Minds/Supernatural) - Castiel has a mission for Emily Prentiss.
Agents and Hunters by sg2009 (Supernatural/NCIS) - People who work in Abby's lab are never what they seem. And Sam is no exception.
Hailing From Parts Unknown by sister_wolf  (X-Men Movieverse/Dark Angel) - Alec and Logan. Cagefighting. Snark. Smut.
Don’t Stop Believing by slaysvamps  (Supernatural/Buffy) - Five times Faith f*cked John Winchester and the one time that she didn’t.
And All the World Beneath by seperis  (Supernatural/Stargate: Atlantis) - Dean remembers Texas as blackland stretching in marker-thick strips of vivid brown and black, broken with the sprawling metroplexes of Dallas and San Antonio and Houston; farms spread with the yellow tops of maize waving in pre-autumn winds, threshers moving complacently through the fields with drowsy men in hats waving at the road. He remembers green and gold fields dotted with cows, half-year calves running on the outskirts of the herds. He remembers these were what he saw between jobs, lives being lived that had nothing to do with creeping twilight and sleeping only behind salt circles and ritual wards.
Eurydice Settlement by vaznetti  (Firefly/Supernatural) - John and Zoe.
Strangers in the Night by theladyscribe  (Supernatural/Scooby Doo) - It's just not the same without Shaggy and his dog.
The What Come Around ‘verse: Manmade Monsters (prequel), What Comes Around (original story), What You See, What You Dream About, What Can Hurt You by spastic_visions  (Supernatural/Dark Angel) - He should have left this city the minute he walked into Crash and saw the double of his brother. Major canon character death.
Bridges by Tassos  (Buffy/Stargate SG-1) - Crossover with Stargate: Xander's real family challenge. After the collapse of Sunnydale, Jack gets a call about a woman he knew over twenty years ago. . . and the son he didn't know he had.
The Ghost of Star's Hollow by vanillafluffy (Gilmore Girls/Supernatural) - When Sam walks into the diner, all hell breaks loose. Or at least, as much hell as a small town in Connecticut can muster; compared to the real thing it's pretty tame. The Winchesters stop for coffee and encounter mistaken identity and a tragic case.
Fire in the Dark by the_ragnarok - Arthur used to be Brendan Frye, a kid who managed to beat Dominic Cobb at his own game while recovering from internal injuries.