Vdirsyncer is a command-line tool for synchronizing calendars and addressbooks between a variety of servers and the local filesystem. The most popular usecase is to synchronize a server with a local folder and use a set of other programs to change the local events and contacts. Vdirsyncer can then synchronize those changes back to the server.
DSynchronize is a stand-alone utility that let you periodically synchronize two or more folders on Hard Disk, Floppy Disk, LAN, USB Key, CD-DVD and FTP server.