I must say there are a couple of features I would like to see included with the calendar.
When you create an event, a topic in a selected forum is created to allow people to comment on it.
RSVP - People can click "Yes, No or Maybe". It then shows a list and also adds it to a block in a members profile page.
My forum is a local community forum, so a calendar to list events I would say is at the very heart of the forum.
Ive achieved the above using a couple of modifications on Vbulletin, however now im making the move over to IPB, I can only see one mod that will link the calendar with the actual forum.
Heres a look at my vb setup. >> http://www.doverlocals.co.uk/calendar.php
When you click on any of the events in the calendar, it takes you straight to a forum topic about it.