Following is a content of a fully functional calendar file
DESCRIPTION:My Description content
This is a really nice concept that I liked very much. If you search for info on "ical" files you will get to browse nice sweet pages including the wikepedia which has nice demonstrations/explations on what this does.
I had a scenario where I had to tinker people's outlook calendar from lotus notes. Using ical files were a really nice option. Atleast I did not find another nicer solution. Once these files are sent to users with the necessary values in it, you can have users open them and save them to their calendars.
A nice way like how xml shall mediate between different platforms. ical - I believe this will work with all major calendars. I know it works for Lotus Notes and Outlook. Yet to test on other web-based stuffs like Google Calendars. Let me know if you test them.