Space
Planet X - Animation shows optimum gravity and temperature for life
Life Cycle of a Star - Quick animation showing the different stages
Orbitiser - nice animation showing inner and outer planets and comets
GPS - a simple animation of how GPS works
LightGrapher is a Flash applet that turns your webcam or built-in computer camera into a makeshift light sensor to display graphically the brightness of a model star (a light bulb or even light-coloured ball).
SimSketch - nice modelling tool to show geostationary satellites