despite the fact that i'm totally listening to Lady Gaga now...
surprised not too many mentions of Pavement's classic, Slanted and Enchanted. great album but i am partial to Crooked Rain x 2. saw them open for Sonic Youth in '92. yeah, it was amazing.
let's see what else that hasn't been mentioned already:
Thrill Jockey bands specifically Tortoise, Sea and Cake, and A Minor Forest.
more Matador. Helium, Bettie Serveert, Come, JSBX, Yo La Tengo.
Kill Rock Stars. Un-fuckin'-wound (two words, "Fake Train"). Sleater Kinney
K. Lois, Heavenly, Beat Happening (ok, pushing it with the "rock" here)
lo-fi that's not Sebadoh. Smog, Palace Brothers, Mt. Goats
Afghan Whigs
Galaxie 500
a whole bunch of stuff on the 4AD, Kranky, Merge labels.
etc, etc, etc...
-Jeff