Andrej Tozon has published the source code of his Silverlight 4 sample project and discusses some of the features that you'll find in this code.
Source: Andrej Tozon's Blog
What’s new in Silverlight 4? Isn’t Silverlight 4, like, old news by now?
Well yes, as the matter of fact, this is one of those long overdue posts that have a hard time getting out. As I’ve been showing these demos since Silverlight 4 Beta came out, this is really the high time I release the source code… Especially when we’re looking to get a fresh preview of Silverlight 5 in the near future.