jurassic 5 is a great starting off point
if you haven't heard it before, Gza's second album, LIquid Swords is incredible, as is Ghostface Killah's Ironman record.
ONxy-Shut em DOwn 98 was anohter good album
Anything Tribe Called Quest is also a good bet
Pete Rocks' CD- SOul Survivor is DEF worth checking out
speaking of Def, check out Redman, and Erick Sermon are pretty good
the Alcoholics from early 90's had some good beats, esp. Hip hop drunkies f/ ODB
if you need any more suggestions PM me, i've got about 250 rap cd's and can give you some ideas as to what to check out, and i'm looking for some stuff i havn'et heard either