Dont know if anyone has heard of this but its pretty freaking awesome. Its good if your at work and what not.
http://www.pandora.com
Its an online radio type thing (no DLing required) just type in an artist or song and it randomly picks artists you might like, and if you dont like them you just click on the picture of the song playing and hit "i dont like it" and it will filter out music like that. Its pretty awesome like i said. Ive heard some good stuff from it since i found out about it today.