I have been looking for a free solution to sync my Google Calendar
with iCal for a while, and I finally found it. A tool is now
available from Google:
"Is having calendar information online, on the desktop, and on a
mobile phone too much to ask? Google apparently doesn't think so
anymore, as the company has quietly enabled sync for Google Calendar,
complete with instructions on how to plug into Apple's iCal.
Thanks to the flexible wonders of WebDAV, or more specifically,
CalDAV, Leopard users can now plug their Google Calendar account
(including those run on Google Apps) into iCal via this simple set of
instructions straight from the Big G's Help Center. Setup involves
plugging a few settings into iCal's Accounts preference pane, after
which the initial sync should happen in a matter of minutes. After
that, any changes made on either end should sync almost instantly.... "