What is "Add to My Calendar"?
If you use a calendering/scheduling program such as Microsoft Outlook, Palm Desktop, LotusNotes, or iCal, clicking on the "Add to my Calendar" link will add the event you're viewing directly into your program as a calendar event. All you need is for your calendering program to support the vCard format and your browser setup to automatically pass the event to your program.
Users of Outlook/Entourage for Macintosh: Outlook and Entourage support the newer iCalendar format. Use Apple's free iCal program to convert the vCalendar file to an iCalendar file.