Soma FM: currently my favorite radio station . Lot's of good ambient, good variety. Definitely thumbs up. Try "Cliquehop" and "Beat Blender."
(the bit-rate on campus usually sucks, but it's worth a try, I promise. You can access Soma on iTunes as well.)
Radio Io: one of the more consistent radio stations. good selections of imports - give it a try. (the commercials are bad ... just turn down the dial)
ioBeat - house music, ambient, etc. (usually better at night)
ioEdge - also very good. indie rock, new music, etc.