Here's a list of popular calendars to try with Google Calendar. Don't click on the links, copy the address and paste it in "Search public calendars" box (you can see the box in the screenshot). Most calendars are in iCal format.
DVD Releases (US)
Harry Potter Important Dates
Lord Of The Rings
Formula 1 2006
FIFA World Cup 2006
For other country's holidays, click the + next to "Other calendars" and go to "Holiday Calendars" tab.
Famous People Birthdays
Find more interesting calendars at iCalShare.
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