I’m never good with music questions, I listen to almost everything.. and I know very little about any of the music that I like. But, I’m going to suggest Atmosphere. Aesop Rock. Also, I’m with @dverhey on Mos Def & The Streets.
Hinterland by aim is a great album. As is Jurassic 5’s LP. De la Soul’s debut album Three Feet High and Rising is a classic. I really like the music of Gorillaz, although it’s not strictly hip hop but has elements. And not forgetting the ladies: Salt and Pepa’s album Blacks’ Magic is another favourite of mine.
Slick Rick, Cypress Hill,Rick Ross, Necro (it can be a bit much but I like some of it) don’t know if Fort Minor or Rage against the Machine count but I like them too.
Also the guys who scratch on the turntables here are sick, called X-Ecutioners they are also a separate group check them out solo too. http://www.youtube.com/watch?v=XtV9ggWmf-I
Oh and forgot about NaS 2 favorites are hip hop is dead and one mic from him.