Music Collection Indexer and Server
Free Web-based MP3 streaming server with an iTunes-like interface
A free and light-weight streaming server for MP3 and OGG files
Open source tool to share your music library over the network with other computers
Open source collaborative music playing tool for iTunes
PyMServ is a graphical client for mserv, a music server.
GMediaServer is a UPnP music media server.
Amarok Shouter will start a small server from within amaroK and serve music streams on a specified port.