Scratch - A free programming tool for kids
This is definitely interesting tool for kids who want to learn how to animated stories, basic games and interactive artworks http://news.bbc.co.uk/2/hi/technology/6647011.stm
Good stuff :) Furthermore based on that article, it would be free of charge.
If someone can do the similar stuff meant for .NET will be great for kids. Less complex and real simple stuff like Scratch. Furthermore from the video, it looks real fun to play with.