Picnic

Picnic is a revolutionary new collaborative file syncing application for Mac OS X to run on two or more Macs on a common local area network (LAN/WLAN).

It offers the ability to create synced folders of files which are automatically synchronized between all users using Bonjour. Use it for syncing a workgroup's files or for syncing your personal files on all your computers.
As such, it offers an easier and safer alternative to file server based shared folders or network drives.