Lala is a music service that lets users listen right inside of the browser. It blends a discovery engine with an online marketplace to let you explore new music and buy the MP3 for playing offline. It also has a service that scans your existing library for tracks in its collection to let you play them from any computer. Tracks that don't match up can be uploaded, so you can still listen to them.
Lala's most famous for its paid streaming service, where users can stream any track once, for free. After that, 10 cents gets you the rights to stream it as much as you want, which covers the license and the cost to get it to you. It's not like purchasing a copy of the track outright, but a whole lot cheaper.