Screenshots

The first two images were taken using iCal on MacOS X 10.3 (Panther). It looks pretty much the same on 10.4 (Tiger). The last four dialogs for subscribing and publishing calendars are from iCal 2.0 on Tiger.

A full week view. The iGroupCal entries are in red. The subject of each appointment is prefixed with the bracketed username. For example, my username is WH, so all my appointments have the prefix [WH]. Week view
Day view A single day view. The two calendars "Home" and "Work" have been published. The "Home" calendar has been published to the special private URL, so the dentist's appointment shows up as "[WH] Private". All the appointments from the "Work" calendar show up as normal, with the user prefix. The other appointments all come from colleague's Outlook® calendars.
Subscribing to the calendar published by the iGroupCal server. Just enter the full URL of the iGroupCal server and any .ics file name you like - they'll all give back the same calendar. Subscribing to iGroupCal.
Subscription authentication. Entering user authentication information in order to subscribe to the shared iGroupCal calendar.
Publishing a calendar to the iGroupCal server. Using a WebDAV style publishing option, enter the address of the iGroupCal server and your assigned user information. Publishing the calendar.
Publishing was ok. Successful publication.