Google Gears - Enabling Offline Web Applications

Google Gears (BETA) is an open source browser extension that enables web applications to provide offline functionality. From Google Site

Google Gears is beta software offered by Google to enable off-line access to services that normally only work on-line. It installs a database engine, based on SQLite, on the client system to locally cache the data. Google Gears-enabled pages use data from this local cache rather than from the online service. Using Google Gears, a web application may periodically synchronize the data in the local cache with the online service. If a network connection is not available, the synchronization is deferred until a network connection is established. Thus Google Gears enables web applications to work even though access to the network service is not present. -- From Wikipedia