http://www.pandora.com is awesome. I needed to share that if you didn’t know already.
Make sure you don’t have a POS machine that dies due to running flash for long periods of time: but this website has singlehandedly saved my sanity for trying to figure out how to play decent mixes of music while I’m at work. Fire it up, and presto. Want to change it up, make a new station. Occasionally you’ll get it stuck in a fairly limited genre of music (I punched in Nirvana and listed almost exclusively to them, Pearl Jam, Stone Temple Pilots, and Live that day) but overall it’s just… awesome.