It’s official: Google Calendar supports Caldav!
http://code.google.com/apis/calendar/developers_guide_caldav.html

Now you can connect to gcalendar using sunbird|lightning referring to url:
https://www.google.com/calendar/dav/UserName@gmail.com/events

Above all, you can have your gcalendar on your mobile using our Funambol Connector
http://sourceforge.net/projects/funambol-caldav

VaUnaSpada!