The Mozilla Calendar project offers their calendar under two different names: Sunbird is a standalone calendar application, and Lightning is a Thunderbird extension. The two are essentially the same, as far as DAViCal is concerned, and these instructions should work for either of them.
At version 0.3 the Mozilla calendar does not automatically refresh the calendar view, so if someone else has added a meeting you will have to manually refresh the view to see that.
It is early days yet for the Mozilla calendar in it's current incarnation so no doubt there are other quirks with Mozilla's handling of CalDAV too, so perhaps take a look at their bugzilla.
As at version 0.3, you should be aware of this bug with empty CalDAV calendars which can be confusing. Add your calendar, create an event and then re-start the program before saying that things are not working!