WPMU is not considered stable yet, although it is in active development. I wouldn't use it for mission-critical projects unless you have the time and skill to put into tweaking it. (James Farmer's edublogs service is a notable example of someone who has invested the time to fine tune things). By the way, if you want a free wordpress blog without worrying about hosting, check out http://wordpress.com/

Magnatune is a record company that offer music licensed in the Creative Commons license. You are able to hear the music before you buy.

Granted, it doesn't have Britney Spears or Moby, but you may be surprised at what you can find there.