Google released a chrome app called Offline Google Mail which allows users to work offline. You can read downloaded mails, reply to those emails and compose new emails. The messages will be send and new messages will be downloaded whenever you get connected to the Internet.
This app was built to function with or without web access. After you install the Offline Google Mail app from the Chrome Web Store, you can continue using Gmail when you lose your connection by clicking the Offline Google Mail icon on Chrome's 'new tab' page.
You can download and install Offline Google Mail from Chrome Web Store. Presently this app is not available for other browsers.
Google will launch offline apps for Docs and Calendar soon..
