Found this link on a blog today - http://warringtonict.wordpress.com/. Warrington ICT seems to be a site dedicated to sharing best practice between school ICT practitioners. It's a treasure trove of great little finds, and I guarantee you'll go back more than once.
It's also got a game called "Magic Pen" whic has to be one of the most addictive games I've seen in ages. You can find Magic Pen at http://magic.pen.fizzlebot.com/.
I remember being in Seattle a few years ago for a week with Microsoft, where one of the things their programmers showed us was an intelligent shape drawing game - you draw a triangle, then draw a ball, and the ball rolls down the triangle.
Magic Pen seems to take this concept way further. Enjoy!