The healthcare prototype source code, which we have demo'ed in one way or another many times, is now posted.   It is a very compelling prototype as far as how a particular vertical -- healthcare -- could take advantage of WPF.  Perhaps most interesting is its different techniques for doing data visualization, including some clever 3D work, which you can see from the screen shot below, as well as some nice video manipulation.  This app is probably one of the more complete samples with source code available on WPF that exists.  The download also includes a script on how to demo it as well as a decomposition of how it takes advantage of WPF, walking through feature by feature. Check it out!