Unison shares a number of features with tools such as configuration management packages (CVS, PRCS, Subversion, BitKeeper, etc.), distributed filesystems (Coda, etc.), uni-directional mirroring utilities (rsync, etc.), and other synchronizers (Intellisync, Reconcile, etc).
rsync is an open source utility that provides fast incremental file transfer.
In Ubuntu you can install from the application menu Grsync, a simple graphical interface for rsync.
SyncToy is a free PowerToy designed by Microsoft that provides an easy to use graphical user interface that can automate synchronizing files and folders. It is written using Microsoft's .NET framework.