phpicalendar  is a PHP tool that parses ics files. Norm Jones [2,3] wrote a script that converts Outlook calendar items to iCal files which are easy to spread among a group with phpicalendar:
The outlook2ical utility is a VB macro that can be used to export a set of appointments from an Outlook Calendar to the iCal format. The end result is a *.ics file. My motivation for developing this macro is that I am not happy with the \”Save As Web Page\” option in Outlook. The main problem is that it saves all appointments associated with an Outlook calendar. I would like to only export appointments of a selected category or categories. I also wanted to be able to view the exported calendar using PHP-iCalendar, which has a far superior appearance when viewed on the web.
Update: Have a look at other tools: http://circle.ch/wiki/CalendarTools