Nextls is a small application that keeps track of your music collection using a MySQL database to store information such as length, bitrate, metadata and where on the harddrive it is located. Everytime Nextls is launched it will figure out any changes done on the file system since the previous run and update the database accordingly. Nextls runs as a shell (console) application and is known to work on both UNIX based systems and Windows.
Only OGG and MP3 are suppored by default and there really are no plans to officially support anything else at this point.
You need the MySQL 5 database and PHP 5.1.3 or later with MySQLi support to run Nextls.
Nx2 is a somewhat complex web application built with XUL that runs in Gecko based browsers, such as Firefox, and act as a frontend to Nextls databases. If you have friends and can convince them to run Nx2 as well you can even connect to each other and share your music.
You need Nextls 5.0, the MySQL 5 database and PHP 5.1.3 or later with MySQLi support to run Nx2.