zlplay is an MP3 player that uses the zlcatalog system to organize songs. zlcatalog is a library for organizing things in non-hierarchical ways. Songs in zlplay can belong to multiple groups. Navigation through the groups shows songs and related groups. So, for example, it's very easy to start listening to all of your songs randomly and then when you hear a song by a particular artist, a single click switches the song list to songs by that artist.
MaGnuX MP3 Control Server is a server that allows you to control the playing of MP3 songs. It uses mpg123 to play the songs, and features playlist management, a builtin Web server, IP-based access control, and much more. It's written entirely in Ruby, which makes it extremely flexible and very easy to extended.
AlsaPlayer-Python is a set of python bindings. It allows you to write custom interfaces for AlsaPlayer using the full power of the Python language. This may be three lines of code or a large and complex interface. Also provided is a Python module to control AlsaPlayer from external programs.
rmp3 is a receiver for the rmp3 broadcast protocol. This protocol uses teletext data transmitted in the VBI (vertical blanking interval) of TV transmissions to broadcast MP3 files. It is compatible with RadioMP3 and the German MegaRadio. You can listen to the audio stream, save the received files, or both.
PrivateRadio is a network jukebox player, collection organizer, and streaming system for MP3 or Ogg music files. It can be used out of the box as just a jukebox, is robust enough for organizing large collections, and is flexible enough to act as a multiple site streaming system with some easy scripting and configuration. It features a radio station metaphor that allows different types of music to be categorized and switched between.