Creating Link on Web Page to Add Calendar Appointment

I want to make an Add to Calendar hyperlink. I'm starting to see these everywhere- most notably on eBay.

What's the easiest way to do it?

Hi maduko,

The easiest way I can think of is to create the appoinment item in Outlook, then save it in either vCalendar or iCalendar format.  Put the resulting file on your web server and create a link to it.  When someone clicks the link it'll open teh file in Outlook as an appointment.  Here's a link to a page that describes how this works in greater detail.
http://www.devx.com/getHelpOn/10MinuteSolution/20508

It only talks about vCalendar format but I believe iCalendar format will work the same way.

Cheers!