Some time ago I came across a solution to sync iCal with Google Calendar (GCal). This is made possible because Google now offer CalDAV for GCal.
I have tested this now for two weeks and it seems quite stable. I just had one event name erased, but this can also stem from the sync with Outlook (yes, I do sync between three different PCs/Macs and this must eventually lead to some data corruption…)
You can find a complete description here.