While previous hints have covered this topic, I have recently cobbled up a solution in order to publish and edit iCal calendars on a WebDAV folder.
It involves a bash script, and an AppleScript wrapper for iCal. I hope this helps someone; I have been using this setup for a while and it works flawlessly, and a lot more reliably for me than the previous solutions...
Mac OS X Hints
http://hints.macworld.com/article.php?story=20060816074311954