coordinating my appointments with someone else is hard enough.

Some offer solution.

http://icalshare.com/ - public iCalendar files

http://www.eventsherpa.com/ - proprietary calendaring application that is iCal based. They want you to host your calendar on their site. Which is also ok.

I also looked on MozCal's calendar sharing ability and thought about using KDE's KOrganzizer. The two didn't agree on the same iCal lingo so I have to wait for newer versions.