Stack identical flat objects so they project over an edge as far as possible
If you have kids below 10, I heavily recommend the Kapla bricks[0]. You find them in nearly all Kindergarten in Germany and kids love them. Our 6 year old son built a 1000 piece bridge with only 4 bricks at the base.<p>[0]: <a href="http://www.kaplaus.com/" rel="nofollow">http://www.kaplaus.com/</a>