I came across Mozilla Prism in a recent version of the SitePoint Tech Times newsletter. The HTML version of this issue can be found here.

The concept behind Mozilla Prism is simple. It effectively allows you to run a web application (or any website) within a stripped down, dedicated web "browser" (I use that term loosely) which enables you to use the web app more like a desktop application rather than a typical website within a normal web browser.

From the Mozilla Labs website:

Mozilla Labs is launching a series of experiments to bridge the divide in the user experience between web applications and desktop apps and to explore new usability models as the line between traditional desktop and new web applications continues to blur. (Mozilla Labs)

This concept is particularly applicable for web applications such as Google Mail (or any webmail system). One noticeable advantage to this new model of use is that it enables the separation of web browsing from the regular use of web apps. If your browser crashes while visiting a site, your web app (e.g. Google Mail) is still running as if it was a completely separate desktop application.

To see what all the fuss is about take a look at http://labs.mozilla.com/2007/10/prism/ to find out more and download the current version of Mozilla Prism for Windows.