Free adaptive/custom internet radio (seriously awesome)
If you've not heard of it...
www.pandora.com Totally free, no malware, bad popups, etc.
You feed it artists and songs that you like and then it custom/adaptively stream music that is similar to what you gave it. Then you can, if you want, say if you like or dislike a song. You can also bookmark songs to keep track of new things you like.
Basically, just has a little ad floating on top of the player, that's it.
I highly recommend it if you're interested in something a little different. It's pretty good in that you can essentially have a free streaming jukebox of stuff YOU like.