Just heard about this today, have not tested it but it was given high praises.

Songbird an open source music player and music organizer, should support the more popular players and formats.

From the website.

The Open Music Playersongbird

Songbird is an open-source customizable music player that’s under active development.

We’re working on creating a non-proprietary, cross platform, extensible tool that will help enable new ways to playback, manage, and discover music. There are lots of ways to contribute your time to the project. We’d love your help!

There are several features we’re proud of, but we’ll be the first to admit that others need ironing out, are experimental, or are just plain missing. There’s still a lot to do.