Windows CE Documentation
My team here at Microsoft also publishes Windows CE documentation - which is distinct from the SDK documentation. It's got a lot of in-depth material, and you might find it interesting reading.
Unfortunately, we forgot to tell anyone that we published it. The most recent update to the documentation was made in August, and you can find it here: http://www.microsoft.com/downloads/details.aspx?FamilyId=2D7E6F80-1BEB-4255-89FE-42CA85856ADC&displaylang=en