AmiTunes is a basic music library manager, loosely modelled on Apple's superb (IMHO) iTunes. Of course it's not nearly as fancy and feature-rich as iTunes, but it does the job. Or, at least, it should do if it ever gets finished...
The project itself started as a front-end to my MP3 Jukebox project, but has since grown and become a project of its own, and so now has its own project page. Click here to visit the project, or click here to jump straight to the downloads section.