KEXP.org
KEXP is a seattle based radio station that also has radio towers in Chicago. They have been streaming online for a VERY long time. They are listener supported like NPR stations. They play the biggest mix of any station I know, all of which i happen to be down with... From underground hip-hop, the dead and dylan, to obscure indie rock and old school punk... it's all in there. they have tons of in-studio events, podcasts, concerts.. they're always doing something different.
When I worked for JASphoto.net I would stream KEXP.org almost every day. Since working on my own this past year, I've been using a satellite connection for internet and it's not very good with streaming media AND using the internet... It may work for 30 minutes or so and then the internet comes to a screeching halt.
Yesterday I was working album designs for PhotosByMarcus.com and streamed KEXP.org all day at his studio... WOW! There is so much I have missed in the last year... i maybe knew a third of the bands they were playing... there's new connor oberst stuff out... i was keeping a list of stuff i need to check out when i get the time.
if you dig (good) music and haven't checked out KEXP before, give 'em a go for a couple hours! The DJs are especially funny too... not morning zoo radio "funny" but genuinely funny.

you can check out their playlists here:
http://kexp.org/playlist/playlist.asp
you can see what they've just played or go all the way back to 2001!
Comments
since reading this, i've been listening to exp today. love it!
thanks