If you're looking to jump into Windows Phone game development, you might want to sit down with this series of ScreenCasts from Tom Mitchell. MangoLander is a Lunar Lander clone, and over the series you'll see how the game is created, with the full source code, and explanations at every critical point.

Here's the first part of the tutorial:

You can follow along with Tom on YouTube on this playlist - currently four parts of the series have been posted, and while we wait for part five there's a lot of programming principles and techniques to learn from the previous parts.