Nextls is a console application that keeps track of your music collection using a MySQL database to store information such as length, bitrate, metadata, and where on the hard drive it is located. When Nextls is launched, it will figure out any changes done since the previous run and update the database accordingly. The database is very simple to work with, and there also exists a sister project in Nx2 that will allow you to take your database online and stream your music from a Web browser.
Cinisis is a PHP library for reading CDS/ISIS databases. It's intended for integrating or migrating existing ISIS databases into other applications. It is a wrapper around other ISIS libraries and tools, providing a uniform interface and iterators for easily fetching data without bothering with internals.