Cool gravity visualization DEC 05 2013
Using a large piece of spandex (representing spacetime) and some balls and marbles (representing masses), a high school science teacher explains how gravity works.
The bits about how the planets all orbit in the same direction and the demo of the Earth/Moon orbit are really neat. And you can stop watching around the 7-minute mark...the demos end around then.
Update: Here's another video of a similar system with some slightly different demos.