KRS-One, Ghetto Boyz, Busta Rhymes, and House of Pain are pretty great. Gotta get some Kurtis Blow and Afrika Bambaataa and the Zulu Nation in there, too, though. Snoop and Dre and Ice Cube as well. Bel Biv Devoe? <_<

Generally for "newer" stuff I go for guys like Ludacris, Wildchild, Madlib/Quasimoto, Heiroglyphics, Deltron 3030/Del the Funky Homosapien, Jurassic 5, Dr. Octagynecologist/Kool Keith, Lootpack, Wu-Tang Clan... I also admit to a soft spot for Kanye West and DMX.

I'm sure there's more than that, but that's all that are coming to me. I love the underground stuff, it's just way better than the popular rap/hip-hop they put on the radio.