PulseAudio is a networked sound server for Linux and other Unix like operating systems.
Open source Mac OS X low latency audio server
PyMServ is a graphical client for mserv, a music server.
streamiumd is a self-contained server that can be used on your Linux machine to serve mp3 files to your Philips Streamium device
KCast is an audio streaming server and GUI playlist editor.
Supercast is a SHOUTcast-compatible streaming MP3 audio server for Unix.
Start a favorite song or recorded voice and let your friends or staffs listen in real time via the Lan or Internet.
Tabula-Musica is a free media jukebox in server/client design.