Sync iCal with Google Calendars - free
I spent a large portion of the day researching calendar sync. I discovered a free and relatively simple way to keep multiple calendar applications across several computers synced together using Google Calendar. It works using CalDAV which iCal started supporting a year ago. I’ve even managed to sync it with my iPod Touch as well.
The only downside to this system that I have discovered is it’s much more complicated to use multiple calendars across iCal and GCal – especially when you add in the iPod sync. I ended up just creating one calendar called Home which I use for everything to reduce confusion. But in the end it’s worth it.
Instructions on Google Support.
Two alternate solutions (which cost money and are probably more reliable):
Spanning Sync
Mobile Me
