Another music recommendation from Jack is a fun way to discover new music through Pandora. You enter a song or artist you like and the site provides you with stations and artists which are similar in composition to that particular style of music. This is the outcome of the Music Genome Project which I couldn't begin to explain to you but you can click on the link and check it out for yourself.
Evidently, I'm a sucker for mild rhythmic syncopation, major key tonality and a male vocal-centric aesthetic. Several of them also had "extensive vamping." What the hell is "extensive vamping?"
I have my stations on the sidebar and you can do the same by clicking on the following link. (I couldn't make a hyperlink with it for some reason.)
Edited to add: Last FM is another site to use to discover new music.