Can you recommend any good communities? Hmmmm. On LJ, the comm I go to for crossovers is strictly for posting stories, not for discussion. batpack is a multi-fandom comm for fic that allows discussion, and it has some really good authors, or buffyfan is pretty laid-back and friendly. My top recommendation, though is Twisting the Hellmouth (http://www.tthfanfic.com). It isn't on lj, but it has a pretty decent forum, and the people there, by default, are into Buffy and crossovers.

Also, your porn star prompt sounds like fun!