Developer website: Martian Technology
SlingShot makes the process of keeping files and now iTunes Playlists in sync between two or more Maces as simple as a few clicks. By incorporating Apple's "Bonjour" technology, SlingShot makes finding and connecting to other computers on a network easy. It's the easiest way to keep your music -- including the expensive songs you've bought from the iTunes Music Store -- backed up and available on all of your computers.
With SlingShot you can Publish an iTunes Playlist of music onto the network and then Subscribe to the Playlist from other computers. SlingShot will copy over any songs from the Published Playlist that aren't in the Subcriber's iTunes Library, add them to the Library, and then recreate the Playlist on the Subscriber. Then it will check periodically to see if the Playlist has been changed; any changes will be reflected in the Subscriber's copy of the Playlist.
SlingShot is also still the simplest way to keep files (and now iTunes music) in sync between two or more Macs. By incorporating Apple's "Bonjour" technology, SlingShot makes finding and connecting to other computers on a network easy. With SlingShot 2.0, it is now easier than ever to share and back up your music collection on all the Macs on a local network.
*Previously available here