definitly buy the new Haiku D'Etat (coup de theatre) cd it's a 'supergroup' i guess you could call it (Aceyalone, Mikah 9, and Abstract Rude) these guys are so sick.
also check out:
LMNO, 2Mex, Afu-Ra, Defari, Atmosphere, the alkaholiks, arsonists, benefit, blackalicious, canibus, bootcamp clik and OGC, handsome boy modeling school cds, el-p, freestyle fellowship, heiroglyphics, souls of mischief, gravediggaz, lords of the underground, pharcyde, masta ace, moka only, swollen members, abstract rude, aceyalone, nas, non phixion, rascalz, fugees, project blowed recordings, zion i, bukue 1..
and everything else that people mentioned.
that should be a good start for you