Shawn Wildermuth has started building his first application for Windows Phone 7, in which he uses for inspiration a couple of Android applications that show the current phase of the moon.
The idea is simple, show the current day's moon phase and let the user swipe right or left to move the current day and watch the moon change phase. To do this I had to get comfortable with Manipulations.
Manipulations are the way that the Windows Phone 7 SDK communicates the touch interface to the developer. Currently the Manipulations are only available to subclasses of the Control class because the 'events' are exposed as protected virtual methods. This is suboptimal but it does work. I hope this changes in later versions of the SDK.