Last.fm is good. It works similar to Pandora.
I listen to Pandora all day at work and it rocks. Help them out and check out their sponsors.
Also, make sure that any time Soundexchange wants to unfairly charge internet radio you get involved.
My Pandora station: http://www.pandora.com/?sc=sh138199648025329030
Seeded with indie rock, a touch of punk, a bit of grunge and some undefinable bands.
Modest Mouse, Built to Spill, Broken Social Scene, Guided by Voices, Cursive, Pearl Jam, Alkaline Trio, and Sunset Rubdown. Many more glorious artists/songs also.