I recently found links at Microsoft's Web site and other sites that launched a prefilled Outlook appointment with details of an event. How can I add such links to my site?
Check the properties of the link. Chances are that the link is to an .ics file. An .ics file is an iCalendar file, a text file that uses an Internet-standard syntax for calendar information. You can create an .ics file from any Outlook 2002 or Outlook 2000 appointment by choosing File, Save As.
Internet Engineering Task Force (IETF) Request for Comments (RFC) 2445 explains the core features of the iCalendar protocol. As far as I can tell, Outlook supports only the VEVENT calendar component for appointments, not VTODO or VJOURNAL, which would be the equivalent of tasks and journal items, respectively. RFCs 2446 and 2447 provide additional information about how iCalendar objects interact between different systems.