Phun is without question the greatest computer toy in the history of the universe… It’s extremely easy to use. As a starter tip, turn gravity off when you’re attaching stuff to the background (right click after selecting “affix” tool).
Very cool for kids of all ages. Kids can learn a great deal just by playing around with this tool – about physics and engineering concepts. This is a great example of technology aiding learning – making it fun and easy for anyone to experiment and see what they can create. Get your Phun (2D physics software) for free. Phun is a Master of Science Theises by Computing Science student Emil Ernerfeldt.
Some other very cool stuff: Cool Mechanical Simulation System – Scratch from MIT