iSynCal

iSynCal is built to synchronize events and to do from iCal calendars between two or more Mac computers using the standard Apple File Sharing.

If you use iSynCal, you no longer need a .Mac account neither to publish your calendars on an external FTP or WebDav server.
You can even use iSynCal to sync your iCal calendars with your iPod or between multiple users on the same Mac.