Google Gears is an open source browser extension that lets developers create web applications that can run offline.
Google Gears consists of three modules that address the core challenges in making web applications work offline.
LocalServer Cache and serve application resources (HTML, JavaScript, images, etc.) locally
Database Store data locally in a fully-searchable relational database
WorkerPool Make your web applications more responsive by performing resource-intensive operations asynchronously
http://gears.google.com/
http://www.labnol.org/internet/tools/web-applications-compatible-with-google-gears/1889/
