Recently, I wrote a batch of articles on Windows Phone for the Nokia Developer Community:
Collection of Value converters for Windows Phone apps
Base functions for Location Based Services in Windows Phone
Finding the right color in Silverlight
Login dialog for Windows Phone apps
How to debug data binding problems on Windows Phone
How to encrypt your application data in Windows Phone
How to store a password hash on Windows Phone
How to turn on vibration on Windows Phone
Preparing for Multi-Platform Apps with Portable Class Libraries