MP3 Sushi is an open source file sharing utility for Mac users.
"MP3 Sushi is a set of two applications: MP3 Sushi Server and MP3 Buddies.
MP3 Sushi Server allows you to turn your Mac into a Jukebox or a Radio broadcast station in a few clicks. It’s a cool way to share and stream your music among a local network or the Internet.
Thanks to the Rendezvous technology (aka ZeroConf), MP3 Buddies makes it easy to find every Jukebox and Radio servers on your local network. Once MP3 Buddies is launched on a user computer, a list of servers is displayed and in just one click the user can browse the Jukebox songs in his favorite navigator or listen to the Radio in iTunes."