Mozilla Labs has introduced Prism 1.0 beta, this is a tool that will enable you to turn websites into applications. You can check it out over here.
Instead of running all your web apps in the browser, Prism lets you run them in their own window just like normal applications. A single faulty app or web page can no longer take down everything you are working on. In the future, we will be releasing web app bundles from the Prism developer community that let you customize your application to use many of the operating system features common to a desktop application.
Prism is based on the same world-class browsing engine as Firefox to ensure maximum compatibility with the entire range of applications available on the web, today and in the future.