This is a fantastic game development environment is free on Windows PCs. We started to create a game and within minutes we had a working version.
Kodu lets kids create games on the PC and XBox via a simple visual programming language. Kodu can be used to teach creativity, problem solving, storytelling, as well as programming. Anyone can use Kodu to make a game, young children as well as adults with no design or programming skills.
There is a lot of information about Kodu online and youtube has lots of Kodu videos and tutorials. One of the best ways to learn it though is to download a project and just jump into the editor and have a play about. There are built in tutorials and I found these to be very helpful in learning Kodu, however, if you want to watch some videos you can do that here.
Here are some helpful links.