On codeplex site is the free e-book dedicated to designing of applications on .NET platform. It's not a reference manual for .NET! This is truly must for every application architects and consultants. What I really like about this book is chapter about Archetypes. It means you can find specific information on rich client applications, web applications, mobile applications(!), share-point applications and many others.
Go and get it here: http://www.codeplex.com/AppArchGuide/
Mobile applications chapter: Chapter 19: Mobile Applications
