A college of mine recently added a WPF showcase on Codeplex. We all need inspiration and this is a great place  to start. Here is not just a showcase of what you can do with WPF, there are panel, custom controls and shader effects. The collection is created along the way to try out various intrinsic of WPF as well as educational. Some has in one form or another made it into working applications.

So go grab it and start experimenting

// Haqwin