If you haven't heard of Grooveshark, it's your next best friend to Pandora. It's the real thing with music on demand... and playlists. You can export playlists too, and embed them in your webpages, like this.
I'm still working out this playlist (and you can maintain several with up to 200 songs), but this one keeps me in a perky mood most of my day. Music and a good mood go a long way in my daily life. Enjoy!