Google has made it a lot easier to share your iCal or Sunbird calendars with others. They are now supporting calDAV with Google calendar. This allows you to set up iCal or Sunbird so that changes you make to your calendar are pushed out to your Google Calendar. Since it's easy to share your Google Calendar, this gives you an easy (and free) way to share your iCal or Sunbird calendar with others.

You can read all the details on how to set this up at http://www.google.com/support/calendar/bin/answer.py?hl=en&answer=99358#