A question needs an answer for most of web developers these days : Can we develop a web application and this application can run out of the browser ? The answer is YES, You can do that.
But How ? Use Silvelight 3.0 Beta.
One of the interesting features in Silverlight 3.0 is that you can detch your application from the web browser and this browser can work as a desktop application.
Silverlight 3.0 Beta have other interesting features such as: checking network availability,storing data offline and much more.
If you have no experience with silverlight 2.0 or earlier, this is the site you want to get started with :
This site is a good reference for all Silverlight 3.0 Features and samples.
Hope this helps.