Grooveshark
Oooh. Me likes! I just found http://listen.grooveshark.com/ and I think it’s cool! You can listen to music via their web interface, create playlists, put music on queue, and share it (Twitter, Facebook, StumbleUpon, email). Its interface lets you discover new music and see what’s hot!
The best part is that it’s a social network. You can find your friends and see what they have been playing, what they like, etc. You can also see people who like similar music you do, people whose music you love, people that love your music – What best way to discover new tunes you may like? =)
They are on Twitter: @grooveshark
Here’s more information: http://grooveshark.com/features