smallfandomfest is a community with the worthy goal of encouraging fanfic and fanart production for lower-profile fandoms. We're not talking about the Treks, Potters, BSGs and Houses of the world, but the fandoms you don't hear from quite so often, or the ones you used to hear about but have quieted over the years, that kind of thing. They have a prompt list for dozens of different shows, movies and books, and the period for claiming prompts and posting the results goes until July 31st. I myself submitted prompts for Buckaroo Banzai, Da Vinci's Inquest, Max Headroom and Miami Vice. They're accepting both fic and graphics, so go wild!
Go here to read the Fest rules, which are pretty relaxed. The prompts are divided between two posts, 10-2001 & A-I and J-Z & crossovers.
Yes, I know I should have pimped this comm while they were still accepting prompts. My oops. *facepalm* But with the wide variety they already have, I'm betting you guys will find something to appeal. Next year I'll get my hype on earlier, I promise. ;)