Mac OS X Tiger/Meet the Applications/iSync
iSync edit
Build in application into Mac OS X for synchronizing (sync) with .Mac, Palms and Cellphones. The sync can be done through cables or wireless using Bluetooth. It syncs all your contacts information and your calendar on phones with such functions.
.Mac edit
If you have a .Mac account (Apple sales tell for about $99.95 on there [Apple Store]) you will have the ability to sync the calendar, contacts.