Gmail Offline is a Chrome Web Store app that’s intended for situations when you need to read, respond to, organize and archive email without an internet connection. This HTML5-powered app is based on the Gmail web app for tablets, which was built to function with or without web access. After you install the Gmail Offline app from the Chrome Web Store, you can continue using Gmail when you lose your connection by clicking the Gmail Offline icon on Chrome’s “new tab” page.
Google Calendar and Google Docs let you seamlessly transition between on- and offline modes. When you’re offline in Google Calendar, you can view events from your calendars and RSVP to appointments. With Google Docs you can view documents and spreadsheets when you don’t have a connection. Offline editing isn’t ready yet, but we know it’s important to many of you, and we’re working hard to make it a reality. To get started using Google Calendar or Google Docs offline, just click the gear icon at the top right corner of the web app and select the option for offline access.
Read more: http://gmailblog.blogspot.com/2011/08/using-gmail-calendar-and-docs-without.html