You can download the latest build of the Mozilla calendar extension or of the Sunbird standalone application from www.mozilla.org/projects/calendar/download.html.
The Usenet newsgroup netscape.public.mozilla.calendar is where many calendar-related discussions and announcements take place.
Some good information about iCalendar files can be found at developer.apple.com/internet/appleapplications/icalendarfiles.html. A more general overview of the iCalendar project is located at developer.apple.com/internet/appleapplications/icalendarfiles.html, although it appears to be somewhat out of date.
Google Maps: maps.google.com