Aimee introduced me to Spotify awhile ago and I LOVE IT! You can listen to WHATEVER you want for FREE! Unlike Pandora you can choose your own playlists. The catch is you can only listen on your computer. You can pay a monthly fee to listen to it on your phone etc if you want.
What I do is listen to what I want on Spotify, then wait for FREE Amazon MP3 credits to come along and buy what I'm not sick of :):):) Works great!