I'm a crossoveroholic m'self, even if I've toned it down A WHOLE LOT in recent years. These days, I usually settle for crossing anime with anime in some slight manner ( Like Kitsune being friends with Tina Foster or the Urashima's being less then fond of Kodachi for assaulting Kanako in the past ) or perhaps just by mentioning something from another fandom then the one the fic is set in ( like Kasumi wearing Azumanga Daioh panties ), or by involving White Wolf's World of Darkness in some manner ( Keitaro becomming Kindred sorta springs to mind ).
Certainly nothing like my older fics set in the Hawkverse, where we have F/X - The Series, X-Files, various Marvel Comics ( primarily X-men, X-Force, Excalibur, Spider-Man and Generation X ), various DC Comics and tv-series ( Primarily Lois & Clark - The New Adventures of Superman ), World of Darkness, THE FRICKIN' POWERPUFF GIRLS, Casca, Remo, Charmed, Kindred - The Embraced, Friends, Tomb Raider, Spawn, Witchblade, Darkness, Street Fighter, Tenchi Muyo, Love Hina, Ranma, Farscape, greek mythology, Aliens, Wing Commander, X-Com, Independence Day and probably even more that I've forgotten all about by now, in one single wonderful Mary Sue:ish world. Now that's an AU.
*shakes head*
I really should devote some attention to some of my unfinished Hawk-fics one of these days, lots of fun to write, they were. Not to mention that I'm still in the middle of revising some of the oldest ones.
Anyways, while I am a fan of writing crossovers, I'm not very inclinded to read crossovers.
Especially certain types of crossovers, R?/SM is for instance something I'd read only if some fic was recommended to me by someone I share similar taste in fics with.
But when I do read crossovers, I prefer crossovers that are at least somewhat compatible to each other ( Unlike my own Hawkverse. I mean, A Mary Sue character, X-Men and the Powerpuff Girls in a darkfic? What was I on when I came up with that idea? ), like say the first and third season of Full Metal Panic and the entirety of Noir. Both are action-packed and set in a corrupt world. The timelines aren't entirely compatible and the tech levels are kinda differing, but it could be made to work without changing all that much around.
Or say the Fumoffu-season of FMP and Azumanga Daioh. Silly little things, both of them, but they could conceivably be made to work very well together with relatively minor changes.
Or Resident Evil and Neon Genesis Evangelion, for something really dark'n gritty.
Love Hina and Aliens? Well, I'd probably check it out for the novelty factor if I came across one, but unless it's really well written, I'd probably drop it before even finishing the first chapter. One is a humoristic school-life romance comedy thingie while the other is supposed to be dark'n gritty horrific thriller-thingie. Unless the transition from the LH comedy angle into a more Alien-like mood is preformed admirably, I'd never finish reading such a crossover.