Here are some useful links you can use to get acquainted with developing mobile apps on WP7:
Download the developer tools here:
http://developer.windowsphone.com/windows-phone-7/
Students can submit apps to the Marketplace for free after they have registered with Microsoft Dreamspark:
A brief High-Level overview of the platform:
http://msdn.microsoft.com/en-us/library/ff402531%28v=VS.92%29.aspx
Some helpful code samples:
http://msdn.microsoft.com/en-us/library/ff431744%28v=VS.92%29.aspx
A very in-depth series of videos that you will probably want to watch:
Happy coding!