Grsync is an open source rsync GUI (Graphical User Interface) which you can use for file and directory synchronization (for backups, etc.). Grsync 1.1.0 was released 2 days ago and it adds some small new features as well as some bugs fixed:

Grsync is an open source rsync GUI (Graphical User Interface) which works on Windows, Linux and Mac OS X. Rsync is the well-known and powerful command line directory and file synchronization tool.

You can use it for easily data backup alongside Dropbox.