Google Gears is a browser extension that allows some web-based services and applications to be used offline, as well as online. Web site developers are able to use AJAX and the Google API to create web applications that work as normal web pages when online, but download usable aspects of the web page in the background so that the web service is usable while offline.
An example of Google Gears in action is the Google Reader RSS reader. When a browser has the Google Gears extension, an icon will appear in the top of the screen indicating that the web site and the browser are synchronized. If the person were to lose the web connection, this icon would turn grey, but the RSS content would still be available. All of this happens automatically, without user intervention.
Google Gears is available for Windows Mobile 5 and 6 devices. To download, visit the Google Gears web site.
Google Gears is also available for Mozilla Firefox (PC) users, and an unofficial port of Google Gears has been created for Nokia Internet Tablet users.
Some websites/web applications that are Google Gears enabled are Google Reader, Remember the Milk, and Zoho.
Developers interested in learning more about how to integrate Google Gears into their web applications should visit the Google Gears API web site.