It seems that this year Google's most popular web applications will work offline. After Google Reader and Google Docs, two other services will integrate with Gears. Andrew Fogg saw a preview of the integration at Google's offices and found that Gmail and Google Calendar will add offline support in approximately 6 weeks.
In the past months, Google accidentally enabled the option in Google Calendar and some users saw the dialog illustrated below: "To view and edit the next 3 months of your Google Calendar when you're not connected to the Internet, click OK."