Leopard server, calDAV, and Mozilla Sunbird
For those wishing to use Mozilla Sunbird with the calDAV server that comes with Leopard, it's not setup in Sunbird in (quite) the same way as it is in iCal.
Let's say you have the calDAV Account URL working in ical (which will subscribe you to all of your calendars) and its URL is
https://somedomain.com:8443/principals/users/username/
In Sunbird, you'll have to subscribe to the your calendars individually. Every calDAV user I've setup so far in Leopard server has been given a default calendar called simply "calendar", which you can subscribed to from Sunbird at
https://somedomain.com:8443/calendars/users/username/calendar/Easy enough. However, if you add a new calendar in iCal, it will create a calendar named with a UUID. In order to figure out what that UUID is, it's easiest to just mount the calDAV in the finder (Command - K) at
https://somedomain.com:8443/calendars/users/username/You'll see several directories in there: calendar, dropbox, oubox, notifications, etc. The one that looks like a UUID (for example, 037D3206-9C1D-4C6C-8E54-B3E3CAF90ABF) is the directory you'll want to subscribe to in Sunbird. In the example above, you would subscribe to
https://somedomain.com:8443/calendars/users/username/037D3206-9C1D-4C6C-8E54-B3E3CAF90ABF/