I have a request/suggestion for people who write crossovers. I don't watch much TV. That's not a snobby 'I don't watch TV' thing, that's a 'I am surrounded by TV and video all day long and I don't want to watch a screen at home' thing. So odds are very very good that I haven't seen one of the shows you're crossing. I'm probably not the only one. So maybe if in the notes/intro you could put in a little blurb about the premise of the shows or something about the characters. Just a line would do. I read a crossover the other day where one of the characters had a name that didn't indicate in any way what gender that person was and nowhere in the fic did the author use anything but the name to refer to the person. I was really disconcerting to read and I ended up going to the IMDB after to see what gender the actor playing the character was.
For example, say I was going to cross Torchwood with Slings and Arrows (and OMG please someone do that and I'll love you forever), I could write:
Fandoms: Torchwood (sort of secret group catches aliens and alien technology in Wales. Capt. Jack Harkness, leader of team, can't die. Ianto Jones, general support, field ops. Jack's lover (canon)), Slings and Arrows (drama/comedy revolving around a Shakespeare festival in Canada. Geoffrey Tennant, director of the festival, normally directs the main stage plays. Somewhat insane and manic. Daren Nichols, totally off the wall guest director.)
Or if that's too much maybe a link to a general info site about the show?