Microsoft released the “MSDN RampUp track for Windows Mobile” Application Development on MSDN — a free online learning program that helps developers to acquire skills in specific technologies and development areas, such as Windows Mobile Development, SharePoint Development and many others. RampUp is completely free. It provides easy-to-access content, in a guided path that defines the important lessons and the order in which you learn them. RampUp content is offered in a variety of forms that allow you to choose the best way to learn; we have articles, codecasts, slidecasts and v-labs. All the content has been authored by well-known experts in the field, such as well-known book and article authors and MVPs.
More info: Windows Mobile track for RampUp