I originally heard about this over Here. I didn't check it out right away though till today and boy have I been missing out. It is like your own personal radio station. It is free, easy, and lots of fun if you have time to play. You just type in a artist or song you like and it will play songs that resemble what you put in. If you don't like a song that is played you click a button that says don't play this again and walla you will never hear it again on Pandora.
Check it out http://www.pandora.com/ I am listening to Norah Jones type music right now as I type this. :) Happy listening