A new service called Counterstream hasn't quite launched yet (it's due to go live in 2007) but its beta service is already turning out to be a really incredible experience in discovering and reacquainting yourself with some of America's most eccentric musical geniuses.
Late yesterday when I listened to Counterstream, I heard John Cage, Duke Ellington, Charles Mingus and Philip Glass, all for free. Right now as I listen, it's Charles Jones, Esa-Pekka Salonen, Easley Blackwood, Ben Johnston and Jeffrey Mumford. Each song that plays has a 'Buy' link next to it, which I assume you'll eventually be able to click to purchase songs from that artist, but doesn't seem to work yet.
Check it out. I'm very impressed so far.
Counterstream Radio [Official Site]

