Verified answer

Underground in the Bay....

Masta Steele

Andre Nickatina

Zion-I

Brother Ali

Hieroglyphics (Soulz of Mischief, Casual, Del, Pep Love etc)

Chilee Powdah

San Quinn (not really underground but he's sick)

The Jacka

The Team (Clyde Carson, etc)

The Federation

Frontline

Top Kat

Just a few.. there's a whole lot more for you to check out.

I'm from NYC, so I'm not sure what's really considered underground out there, but here are some Cali heads definitely worth listening to:

Planet Asia

Rass Kass

Dilated Peoples

Beat Junkies

Pharcyde

Alkaholiks

Dr. Doom

Sick Jacken (Psycho Realm)

Hitman

Defari

Krondon

Holocaust

i live in the east coast listen to this boy wale from D.C. he's WAY WAY harder then most other east coast rappers anywayz try his myspace or somthing

Potluck

they kind of got a bone thugs sound to them in some of their songs. pretty much just rap about smokin weed. big fat black guy called 1 ton and a little tiny white dude called under rated. check 'em out on myspace.

http://www.myspace.com/potluck

Listen to ya boy

try Aman or Paris

Skillz - "he don't own me" (for real).

i love that song :D

http://www.worldofundergroundhiphop.com/

two words:

immortal technique

ASL?