Each Mac running GarageTunes on your LAN can be used as speaker from every other client. This allows you to play songs from any sources on any Mac in your household or firm. Since GarageTunes is library-less and based on spotlight there's no need to add songs to GarageTunes manually or to organize an additional music collection. All mp3 and AAC files on your Mac, on Macs in your network and connected hard drives will be shown automatically (not only your iTunes library). Songs are dynamically updated as Macs connect to your LAN or external hard drives connect to your Mac.
Note: The downloadable version is 1.2b2. The demo version is 1.1. The Mac App Store version is currently 1.1.