Following its introduction for Google Apps customers early last month, the search giant has now made offline Google Calendar available to all. The same previously mentioned limitations apply - users are not allowed to add or edit events while offline plus apparently not all entries are downloaded - and of course it requires the Google Gears plug-in to work.
To activate the feature head to your calendar page and hit the "Offline (beta)" link on top to start the syncing process. Note that the first sync only applies to your main calendar, though in the Offline Settings page you can change this to include other calendars as well. It is a limited offline calendar solution for now but this is definitely a nice addition for those who rely on Google's services on a day to day basis.