This week I downloaded Xamlon, and it is really cool. When you install it, I automatically adds an add-in to VS 2003 so that you can create Windows Forms apps with XAML. XAML replaces the normal Windows Form as the UI for a desktop application. Normally talked about as a UI technology to be shipped with Longhorn, xaml has been implemented in Xamlon and is available now for Windows. When you create an application with Xaml, you still have your code behind in .Net and your logic in supporting classes, but you just have a completely different way to make your UI. You desktop UI is markup. ASP.NET developers will love this new flexibility in desktop programming. No longer do desktop applications have to be rigid and absolute-positioned. Now they can flow with the size of the window. Xaml also makes use of vector-based graphics instead of raster-based graphics. In your Xaml UI, you can create lines and shapes by defining them with markup, and they can scale easily. Xamlon comes with some examples of clipart that are nothing more than markup-shapes. They scales to any size because they are rendered as vectors, not pixels.
Xamlon is really cool. I suggest that you check it out because I believe that in 5 years, Xaml will be the preferred desktop UI for new applications.