oh dear god where to begin. I guess I'll just post some youtube vids of artists you might like but I could go on for days recommending artists to you.

YouTube - Uyama Hiroto - Vision Eyes ft. Golden Boy
YouTube - Blue Scholars - Sagaba
YouTube - MF Doom (Madvillain) - Accordion
YouTube - MF Doom - Doomsday
YouTube - Kid Cudi - Daps And Pounds
YouTube - nas new york state of mind 2
YouTube - Bad Mutha - Lord Finesse & DJ Mike Smooth
YouTube - Nujabes - Think Different (feat. Substantial)

That's a pretty good start.

if you want something a bit more raw i.e. pure rhyming madness and intensity, check out:

YouTube - Kool G Rap & MF Grimm Freestyle - Stretch & Bobbito Show '95
YouTube - Big L - '98 Freestyle

(these are slightly more profane)