Have you checked out www.pandora.com yet? If you go there on your PC, iPod or iPhone and key in your favorite musical artist, in seconds the site will create your own personalized radio station that plays that artist's tracks, along with tracks by other artists you might like. For instance, I recently typed in Frank Sinatra, immediately heard the Chairman's Nice & Easy (from the album of the same name), followed by Dean Martin's You're Nobody 'Til Somebody Loves You, Bobby Darin's Beyond the Sea, with more Sinatra after that. It really is a cool site.
There's some commercial interruption, but it's minimal. When I last listened earlier today, there was a short Ace Hardware ad every eight or nine songs or so, and that's it. It even works with classical music and movie soundtracks: just type in a classical composer like Mozart or a movie composer like John Williams and have fun discovering what the site puts together for you. Give it a whirl!