The first demo of Gears will be for Google Reader, but more Google apps are expected to come. Reader will add a green download button to the user interface. When you click the button, Reader will download the last 2,000 messages to your computer, preparing your computer to work offline or under a spotty internet connection.
Google is releasing opensource and early to developers to get some preliminary feedback. They are also collaborating with a host of other partners such as Opera, Mozilla, and Adobe, which will to integrate flash and Apollo into their system.