Google Gears

Google Gears is an open source browser extension that lets developers create web applications that can run offline.There are three core modules provided by Gears: a LocalServer for storing and accessing application pages offline, a Database for storing and accessing application data on the user's computer, and a WorkerPool for performing long-running tasks (such as the code that synchronizes data between your server and users' computers). You can also use it to download URLs for later viewing. It looks like a very useful tool for web developers and for general offline viewing of pages say if you live where there is no internet access.