ProgrammableWeb lists many popular Music APIs in the directory including Last.fm, 7digital and Spotify Metadata. This post features a few really creative, entertaining mashups that use a few popular Music APIs.
Somewhere out there is a singer-songwriter who could use your code. And who knows, that artist--or one of the other more than 10,000 on ArtistData--might even pay you for it.
ArtistData is a site to help musicians store their information and reach out to fans in the shortest amount of time. For example, enter tour dates once, then publish to MySpace, your website and send local media alerts.