Did you ever make a "tornado jar"? →[More:] I was just explaining this concept to the husband while washing out a mayo jar about to be recycled. He never made one- I remember making several throughout my childhood, and I was always totally fascinated by 'em. I'd keep them until the soap broke down and wouldn't form the "cloud" anymore.

Basically you take a mayo jar, fill it most of the way up with water, add some dish soap, and drop in a marble. Cap it, and you can swirl it around to make a little "tornado" inside the jar.

Good for kids who will eventually grow up to love science, storms, fractals, and LSD.