If you're a student and you want to get involved in developing apps for Microsoft, then this page is for you. I'm going to outline and maintain all the resources I know about that are specifically designed to give you free software, train you, and prepare you for making great apps on Windows and Windows Phone.
Install Scirra Construct2 game engine: http://www.scirra.com/construct2
YoYo GameMaker game engine: http://yoyogames.com/studio/download
Install Unity game engine: http://unity3d.com/unity/download/download-windows
InkScape vector graphics editor: http://www.inkscape.org
I'll likely have far more resources here in the future. If you need any help getting your system app ready, just let me know.