iCal and Google Calender synchronization is something that many people want. We've recently looked at Spanning Sync, which gets the job done (Spanning Sync is currently in beta).
Today, TUAW reader Jim has pointed out gSync, another application on the scene. I played with it briefly this morning, and it seemed to work well. It's a little less polished than Spanning Sync, but still use-able.
To tell you the truth, I'm content to use my Google Calendar for my day-to-day activities and just keep iCal as a reference. But that's me.