Art Gorski passes along helpful information, "Apple's iCal has long had the ability to subscribe to publicly shared Google Calendars, allowing you to view these calendars in iCal. This still required the owner to login to Google to edit these calendars. The Snow Leopard version of iCal has added the ability to sync with Google Calendars, allowing the owner to edit these calendars in iCal and having the changes automatically sent to the Google Calendar. To do this, select the menu iCal > Preferences and click on the Accounts tab. Next, click on the '+' button at the bottom of the window to add a new account. Enter your Google Email address and password credentials, select 'Google' from the pulldown menu, and click the Create button. Under the 'Delegation' tab you can specify which of your Google calendars you want to appear in iCal."