This procedure comes from trying to find a way to use MobileMe to somewhat securely publish a calendar and there may be more security levels available than are mentioned here.
- First, turn off calendar syncing in the MobileMe prefpane (System Preferences » MobileMe » Sync) so it won't be fully public.
- In iCal, go to Calendar » Publish... » Publish on: A private server
- Publish your calendar to following private server URL:
http://idisk.me.com/username/Shared/MyCal.ics, inserting your username and substituting the calendar name you want for MyCal. - You enter your MobileMe username and password as necessary.
- The published URL will be webcal://idisk.me.com/username/Shared/MyCal.ics, once again substituting your username and calendar file name.
[crarko adds: I haven't tested this one. Apple has recently made changes to MobileMe which may or may not affect this hint.]

