Andy Wigley, Daniel Moth, and Peter Foot have been hard at work developing an MS Press book called Microsoft Mobile Development Handbook (link to Amazon) - the book (all 688 pages of it!) covers the following topics.
1. .NET Compact Framework—a Platform on the Move2. Building a Microsoft Windows Forms GUI3. Using SQL Server 2005 Compact Edition and Other Data Stores4. Catching Errors, Testing, and Debugging5. Understanding and Optimizing .NET Compact Framework Performance6. Completing the Application: Packaging and Deployment7. Exchanging Data with Backend Servers8. Networking9. Getting Connected10. Security Programming for Mobile Applications11. Threading12. Graphics Programming13. Direct3D Mobile14. Interoperating with the Platform15. Building Custom Controls16. Internationalization17. Developing with Windows Mobile18. Introducing .NET Compact Framework Version 3.5 and Visual Studio "Orcas"
If you are developing applications for Windows Mobile devices then you should consider getting a copy of the book.