Magnatune: try before you buy MP3 music.

Discovered this site through a listing in the creative commons blog.
From the site promo:
We call it "try before you buy." It's the shareware model applied to music.

Listen to hundreds of MP3'd albums from our artists. Or try our genre-based radio stations.

If you like what you hear, buy our music online for as little as $5 an album or license our music for commercial use.

Artists get a full 50% of the purchase price. And unlike most record labels, our artists keep their rights to their music.
Founded by musicians, for musicians.

No major label connections.

We are not evil.

I hadn't really considered buying music online but this is a pretty good model. You pick how much you are willing to pay for the album and then download the entire album in .wav or mp3 format. No licence restrictions etc. Some great music available.