Patterns and practices has put on the Visual Studio Gallery a set of layer diagrams which correspond with the Application Architecture Guidance…
http://visualstudiogallery.msdn.microsoft.com/en-us/237f823c-45b4-4f1f-b9e2-607fe66eaae7
Install the VSIX in VS2010 Ultimate and you get diagrams like these, with all the validation capabilities the layer diagram has.
And the corresponding guidance…
Very Nice work…