This means that you can now use iCal with Google Calendar, allowing you to work offline, sync almost instantly, respond to invitations from others and see the free/busy data of your friends and coworkers.
We launched CalDAV support to our developers last July for feedback, and since that time a few of us whipped up a nifty setup program for iCal. This tool makes it a breeze to get iCal working with your Google account. We've released this as open source and the program is available for download at our Google Code site.