Ones that actually officially put a full project out
Slaughterhouse
The Weathermen
Random Axe
Gravediggaz
La Coka Nostra
Westside Connection
The Firm
EMC
Prophets of Rage


Or ones that only put out a few songs, bootlegs, etc.
Golden State Warriors (Saafir, Xzibit, Ras Kass)
Four Horsemen (Killah Priest, Canibus, Kurupt, Ras Kass)
Black Hockey Players (Co$$, Blu, Planet Asia, Ras Kass)
MARS (Cormega, Action Bronson, Roc Marciano, Saigon)
Crooklyn Dodgers
CRS
All City Chess Club
Bad Meets Evil
Fantastic Four/Psychic Friends
Murder Inc
Indelible MCs