Just came over a few mp3 acapellas - including aesop rock, mf doom, quasimoto, dj vadim, slum village, the perseptionists and many mores. Download mp3 using links. Acapellas are good if you making remixes, or just to check the way your instrumentals sound with some rappin'.
If you're looking for something else, i may try to help. And if you got some Stones Throw acapella (Wildchild, Madlib, Quasimoto, Declaime, etc), i'd be grateful.