The Windows Phone 7 development articles are now published. They are aimed at guiding you through all the fundamentals of WP7 development, starting with “Hello World”. The topics are presented in a recommended order for newbies (like chapters of an intro book); however, they are also designed to be modular, so you can skip around to learn about specific tasks and features. The content uses a lot of code snippets along with screenshots, videos, and even embedded Silverlight to demonstrate how the code behaves.
[updated to correct the link - sorry!]