Quick Google Calendar Tip: Add by URL

"Adding public and friends’ calendars to your own Google Calendar account is quick and easy, as we have explained before. But what if the information given to you was a URL only? For instance, an organization may publish their public calendar’s URL in iCal format.

With Google Calendar, it’s also easy. First, of course, you need the exact URL of the public (or private!) calendar you wish to access. ..."

http://www.googletutor.com/2008/03/17/quick-google-calendar-tip-add-by-url/