Hey, I just recreated a couple of my comms from LJ over here and thought I'd pimp them a little bit.

spn_random is a writing challenge comm for Supernatural/Crossover pairings. You choose a character from Supernatural and another character from any other fandom of your choice and write fic based on a set of prompts.

spn_roadside is a writing challenge comm, again for Supernatural, where the author writes fic for prompts based on roadside attractions, historical landmarks, or other things of that nature.

and finally,

fairytale_redux is a multi-fandom challenge community where either an author or artist choose a Brother's Grimm fairytale to rewrite for a fandom of their choosing.

Everyone is welcome to participate, so stop by and check it out!