Always on the hunt for replacements to the functionality that dot mac used to try to provide me, I decided to try out CalDAV. I chose the implementation by Apple, released as Open Source on MacOSForge.
Using these instructions, it was easy to install.
In short order, I had it installed, running on HTTPS with a self-signed certificate. A bunch of users and locations setup and ready to go.
Leopard comes with a built-in CalDAV client, the iCal application, I only have Leopard installed on one machine ATM (I have CalDAV running on an old Cube under Tiger), so wanting to experiment with sharing, I invited by brother in Australia to join me.
Once you have added your Cal Server account in iCal, it is as easy to create new calendars on the server as it is locally. I am confidant that when I have more machines running Leopard, they will all be able to share the same calendars between them.
Sharing a single user's calendar between multiple users is still a problem though. According to the plan, you ought to be able to assign levels of sharing in your own calendars from the client, this does not seem to work yet as far as I can tell.
My brother and I can share a calendar, and it works well, but in such a way that it has to be setup in advance via server configuration. I made a 'location' and added our two users to it. We can both add, edit and delete each others entries. We have not tried any of the auto-scheduling features yet.
I do not have access to Leopard Server, so I do not know if the version of Calendar Server that comes with it suffers from the same problems, but regardless, the free MacOSForge Calendar Server is already a very useful tool for any workgroup, club, family or individual with more than one computer (CalDAV is a cross platform standard).
If you have a server knocking around, give it a go :)
PS. I am spending the next two weeks in Holland doing some work. I will know pretty soon just how good or bad it is to be on the road using a remote calendar !!