Does anyone know of any good websites/sources that deal in instrumentals, acappellas or separates audio tracks for people to remix?

A google search just gave me an endless list of pages regarding bad r'n'b/hip-hop remixes, and I'm pretty sure I personally can't be bothered to remix Gucci Mane, Lil' Jon or 50 Cent, etc etc...

Anyone who dabbles in remixing, where'd you get your source material from? Any help would be greatly appreciated! Thanks.