The Following are excerpts from From PhET.com
Move the sun, earth, moon and space station to see how it affects their gravitational forces and orbital paths. Visualize the sizes and distances between different heavenly bodies, and turn off gravity to see what would happen without it!
Visualize the gravitational force that two objects exert on each other. Adjust properties of the objects to see how changing the properties affects the gravitational attraction.
Can you avoid the boulder field and land safely, just before your fuel runs out, as Neil Armstrong did in 1969? Our version of this classic video game accurately simulates the real motion of the lunar lander with the correct mass, thrust, fuel consumption rate, and lunar gravity. The real lunar lander is very hard to control. -- Note this is a Flash Simulations and requires you to enable Flash.
Build your own system of heavenly bodies and watch the gravitational ballet. With this orbit simulator, you can set initial positions, velocities, and masses of 2, 3, or 4 bodies, and then see them orbit each other. Note this is a Flash Simulations and requires you to enable Flash.
This is a crash course of Plate Tectonics with videos -- What moves the crust? Plate boundaries, and mantle/crust alignment, Oceanic and Continental Plates,
This simulator shows images of the planets at different times and locations. You ca ntarget and date show how the planets is seen on any date -- you can change UTC Field of View, and change the field of view of degree(s). Options you can change include percent of the image width -orbits -extra brightness...Frequently asked questions about this simulator.
PhET -- Founded in 2002 by Nobel Laureate Carl Wieman, the PhET Interactive Simulations project at the University of Colorado Boulder creates free interactive math and science simulations. PhET sims are based on extensive education research and engage students through an intuitive, game-like environment where students learn through exploration and discovery.