DanceBox is a fork of the pyTone jukebox highly customized for a dance studio. It features an advanced SQLite classification database that should rival commercial offerings.
libtagedit provides a C++ and python interface to music file tag editing which should be as easy as possible. It has a plugin structure and is easily extendable. Currently, it includes plugins for MP3 (ID3v2 r/w and ID3v1 reading), OGG and FLAC files.