Spotify, the new Grooveshark! (move over)
Reasons this player rules the world:
- Play almost everything on the fly
- Facebook account integration. No need to sign up.
- Remembers your music, and suggests related artists which lets you discover new music
- It's like having your own iTunes with all the world's music in it.
- It's free, I don't mind having ads on it. (It's a small frame on the window anyway)