As was the case with cloud computing in general, I'm way behind on this one, but Mozilla has a project called Prism (previously WebRunner) that lets users split web applications out of their browser and run them directly on their desktop. This sounds really promising and it works really well, even today:

Personal computing is currently in a state of transition. While traditionally users have interacted mostly with desktop applications, more and more of them are using web applications. But the latter often fit awkwardly into the document-centric interface of web browsers. And they are surrounded with controls–like back and forward buttons and a location bar–that have nothing to do with interacting with the application itself.

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.

The first of these experiments is based on Webrunner, which we’ve moved into the Mozilla Labs code repository and renamed to Prism.

Prism is an application that lets users split web applications out of their browser and run them directly on their desktop. Prism lets users add their favorite web apps to their desktop environment. When invoked, these applications run in their own window. They are accessible with Control-Tab, Command-Tab, and Exposé, just like desktop apps. And users can still access these same applications from any web browser when they are away from their own computers.

We’re also thinking about how to better integrate Prism with Firefox, enabling one-click “make this a desktop app” functionality that preserves a user’s preferences, saved passwords, cookies, add-ons, and customizations. Ideally you shouldn’t even have to download Prism, it should just be built into your browser.

Related: Prism on the Mozilla Wiki