This is one application I have developed for WP7. It is a map of the night sky and at the same time a three dimensional map of the nearest stars. You can switch between a view from the Earth and a Space view of the nearest stars. A 3D view of the solar system is coming soon. This is a link to the Windows Phone Marketplace: http://social.zune.net/redirect?type=phoneApp&id=960d8167-c43c-e011-854c-00237de2db9e

The website for the project is http://www.stars-3d.com/

A short introductory video can be found on YouTube at http://www.youtube.com/watch?v=UmdW6rH2K0o and also another one at http://www.youtube.com/watch?v=0pCtfvLPLZw