Conduit is a synchronization program for GNOME. It allows the user to synchronize data to and from various destinations. (GPL)

Gnomad is a GTK+ client program for the NOMAD Jukebox. (GPL)

Hipo is an application that allows you to manage the data of your iPod. (GPL)

rsync is an open source utility that provides fast incremental file transfer. (ZPL)

Create Synchronicity is an opensource application developed in VB.NET to synchronize files and folders across different locations. (GPL)

Unison is a file synchronization program. It is used for synchronizing files between two directories, either on one computer, or between a computer and another storage device. (GPL)