Iwascoding has released GarageTunes (http://www.iwascoding.com/GarageTunes/), a collaborative music player application
for Mac OS X 10.6 and higher. It’s available at the Mac App Store for an introductory price of US$4.99..
According to the folks at iwascoding, GarageTunes finds all the music files on connected hard drives without the need to maintain a special library or pointing it to a certain directory. Plus, it shows all music files on other Macs running GarageTunes in the same network in a single view. Finally, any Macs on the local network can be instructed to play songs stored on any other Mac running GarageTunes.