http://www.pandora.com/

Just checked this out, nice little gadget so far.
Lots of potential.

I need broadband in my car now.

It reminds me of the "radio stations" in Rhapsody. It's usually the way I broaden my music library. I listen to artist in the same genre in the radio feature and when it plays something I like I follow the links to more stuff by the same artist and follow more links to the artists that are their contemporaries and their influences. It's a great way to find new music.

That is very nice.