MultiSync is a free modular program to synchronize calendars, addressbooks and other PIM data between programs on your computer and other computers, mobile devices, PDAs or cell phones.
Now have modules for:
Ximian Evolution synchronization, supporting calendar, ToDos and contacts.
IrMC Mobile Client synchronization (supported by e.g. SonyEricsson T39/T68i, Siemens S45i/S55 phones etc.) via Bluetooth or IR on Linux, or cable connection.
Windows CE / Pocket PC synchronization.
Opie and Zaurus synchronization.
Experimental SyncML support.
Remote connection of two MultiSync programs via an encrypted connection over the net. Perfect to synchronize your laptop and stationary computer, or why not your home and work calendars?
Backup of your PIM data.