This article is an absolutely awesome review of the different Web sites out there where you can listen to the music you love for free. My absolute favorite out of the eight reviewed is Pandora, and I listen to it at home and the office. It is absolutely amazing.  

About six years ago, a group of musicians and music-loving technologists came together with the idea of creating the most comprehensive analysis of music ever. They did comprehensive analysis of more than 10,000 different artists -- ranging from the popular to obscure -- analyzing the musical qualities of each song one attribute at a time.

You pick your favorite song and they create a station for you that includes many songs and artists of which you've never heard. However, what's collected for you to hear is very similar to your original song, and you can further train the system by telling it if you like or dislike the songs it chooses.

And, if you like the music you hear on Pandora, you can learn how to save those songs to your hard drive.  

If you like music, you will love Pandora.