My friend Jürgen Hubert, Author of Doomed Slayers, has been running a project for a while now which he describes as "The Wikipedia, for gamers by gamers!" His goal was to produce an encyclopedic resource for role-playing games that would distill useful factoids from the real world that can be used as plot ideas for Game Masters.
It's an ambitious project, and after six years is still far from the encyclopedic resource Jürgen hopes for, but there is a lot of fun, weird and eclectic stuff on it.
(And, fair disclosure, yes, I am one of the contributors to it).
Here he gives a good explanation and introduction to the Arcana Wiki: My Gaming Projects Part III: The Arcana Wiki ; and here is the site itself: The Arcana Wiki
It's a fun site; although you have to be careful about clicking on the Red Links (which don't go anywhere yet and will just frustrate you). I recommend reading Jürgen's introduction first.
Oh, and check out Doomed Slayers. It's an interesting look at the traditional clichés of Dungeon Delving that manages to put them in a reasonable social context. And I hear the artwork is keen.