I really find the upcoming DVD on the Home Page helpful. If you added an 'Add to Google Calendar' link it would be really helpful for those who use the great Google Calendar and would forget when the DVD will be released, and would probably help more people to use the Google Calendar.
Its very easy to make this happen, http://www.google.com/googlecalendar/event...html#individual describes the process but http://deepak.jois.name/gcalevent/ makes it very easy.
At the moment I do not believe that is possible with Yahoo though.