I just discovered this interesting book on "Programming Windows Phone 7", by Charles Petzold (yes, that's the author of the famous "Programming Windows" series of books). This Microsoft Press title is available as a free PDF download and is over 1,000 pages long.

Here's the table of contents:

• Part 1: The Basics
  • Chapter 1: Hello, Windows Phone 7
  • Chapter 2: Getting Oriented
  • Chapter 3: An Introduction to Touch
  • Chapter 4: Bitmaps, Also Known as Textures
  • Chapter 5: Sensors and Services
  • Chapter 6: Issues in Application Architecture
• Part 2: Silverlight
  • Chapter 7: XAML Power and Limitations
  • Chapter 8: Elements and Properties
  • Chapter 9: The Intricacies of Layout
  • Chapter 10: The App Bar and Controls
  • Chapter 11: Dependency Properties
  • Chapter 12: Data Bindings
  • Chapter 13: Vector Graphics
  • Chapter 14: Raster Graphics
  • Chapter 15: Animations
  • Chapter 16: The Two Templates
  • Chapter 17: Items Controls
  • Chapter 18: Pivot and Panorama
• Part 3: XNA
  • Chapter 19: Principles of Movement
  • Chapter 20: Textures and Sprites
  • Chapter 21: Dynamic Textures
  • Chapter 22: From Gestures to Transforms
  • Chapter 23: Touch and Play

If you're interested in developing applications for Windows Phone 7, make sure to download this e-book from http://charlespetzold.com/phone/index.html