Have you seen slacker.com? It's another online music radio source (like Pandora or last.fm) -- but it's more in the radio mode than the other two.
The home page shows various types of radio stations / genres, broken out by TOP Stations, ALL stations, and Custom stations. The default is TOP stations, which includes the usual stuff you hear on the radio: 60s, 70s, 80s, 90s, 00s, and any combination of those, plus Adult Alternative (playing Elvis Costello from My Aim is True right now, and including Aimee Mann, Bob Marley, and more), Country, Oldies, etc.
For me, the ALL stations link is more interesting. I like the Folk / Folk tab, which includes Lucinda Williams, America, Bob Dylan, and Ben Harper. Some nice Joan Baez is playing now; seems that Love is Just a Four-Letter Word. Sadly, "International" seems to mean UK -- I'd like to see some French, Indian, Caribbean, and African. Maybe that's coming.
Looks like Slacker can also send music to your portable player, and the Times article says a version is coming for your car. Right now it's free (maybe with ads?) and you can get an ad-free version for $$.
One thing I really like about this? The web page title shows the name of the song, artist, & album so you can quickly tell what the song is & who's singing it. It also tells you what's coming next. You can add & delete artists from "your" radio station.
Found from this New York Times article: Technology: Now, a Radio Station for (Your Name Here)
By J. D. BIERSDORFER, March 15, 2007.
"Aimed at the music lover who does not want to fritter away hours creating playlists, Slacker offers millions of songs grouped into radio stations by genre or artist."
Warning: this looks like it could eat up a lot of time ... but provide much musical entertainment along the way.
np: Cigarettes & Chocolate Milk, by Rufus Wainwright from Poses.