Rat Creature's Journal

Nothing Like Billy, by Embroiderama. Het, Ellen Harvelle/Fox Mulder. (ca. 2,622 words)
Supernatural/The X-Files
There isn't much plot beyond the sex in this crossover, but there was enough characterization and a plausible reason for their meeting to not have the story feel arbitrary.

Leapin Lizards, by Gwendolyn Grace. Gen, Sam Winchester, Dean Winchester, Sam Beckett, Al Calavicci. (ca. 18,560 words)
Quantum Leap/Supernatural
Sam Beckett leaps into John Winchester when Dean and Sam were still children. There is a good case story, and Beckett has to deal with finding out that the supernatural is real, and handle two young Winchesters.

With a Bang, by Mink. Gen, Alec, Dean Winchester, Sam Winchester. (ca. 42,000 words)
Dark Angel/Supernatural
This is a good action-adventure, and I liked how the shows' mythologies were meshed, even though I'm not that into the whole breeding cult arc of DA season two. Also Alec, Sam and Dean together are just fun to watch.

Curiosities (ca. 4,045 words) and Stutter (ca. 1,500 words), by Penknife. Slash, Erik Lehnsherr/Charles Xavier, Tom Riddle, Lily Potter, Sirius Black.
Harry Potter/X-Men
Recently Penknife offered to write timestamp fic, and I noticed that I never recced the original crossover for which I requested a timestamp. Anyway, in the first Erik Lehnsherr encounters Tom Riddle in 1950, the timestamp is set during the first Voldemort war/the Marauders era, and both are interesting and well worth reading.

Brothers in Arms, by SylvanWitch. Gen, Dean Winchester, Derek Reese. (ca. 2,440 words)
Supernatural/Terminator: The Sarah Connor Chronicles
Dean runs into Derek while hunting, and somehow these two shows just go together like chocolate and hazelnuts.

What Kind of Day Has It Been?, by Victoria P. Gen, Dean Winchester, Sam Winchester, Kermit and the Muppet Show ensemble. (ca. 3,300 words)
Muppet Show/Supernatural
I love Muppet crossovers (felt rules! *g*), and this one made me laugh a lot.

I updated my crossover recs page.

Old Country, by Astolat. Slash, Sam/Dean. (ca. 40,600 words)
Harry Potter/Supernatural
I don't read a lot of Wincest, but I think this crossover is a great read even if you prefer gen. It's a lot of fun, humor mixed into the angst and drama, and the merge of the Potterverse with SPN here works great, and I liked the take on goblins and their magic in particular.

Harvester of Eyes, by gwendolyngrace. Gen. (ca. 26,000 words)
Sandman/Supernatural
John Winchester hunts the Corinthian, meanwhile Sam and Dean get lost in the Dreaming. This crossover is a great blend of the two sources.

New Jersey Voodoo, by Rokeon. Gen. (ca. 1,020 words)
House/Stargate: Atlantis
This is short, but really funny. John has a relapse back towards Bug!John, starting with an at first innocuous rash and progressing from there, and House tries to diagnose.

Late Nite at the Sudzy Dudz, by Sarah Ellen. Gen. (ca. 3,500 words)
Supernatural/The X-Files
I have no idea how I could have missed reading this story for so long. This crossover is a lot of fun. I guess you could sum it up as "Mulder and Scully meet the Wincesters in a laundromat and talk about cattle mutilations." but the dialog is awesome and it made me laugh a lot, while still being plausible and in character within both series.

The Curious Incident of the Doc in the Night-time (part 2), by Taz. Gen. (ca. 2,920 words)
Highlander/House
House meets Methos in his morgue and is understandably curious. Snark ensues.