The WPF team have released an interesting document called the WPF Application Quality Guide. You can download it as a .doc file from that page, or just read it on line. It's an intruiging combination of handy links (Getting Started with WPF), overview diagrams, philosophy and advice around testing and development that would apply to non WPF projects as well, and very WPF-specific practices (should I derive from Control or UserControl?) aimed at testers and developers alike. The Word version runs to almost 80 pages but not all the sections will apply to every reader. You should take a look at it, for sure.