Interactive NASA Observatorium on satellite orbits and Kepler's Laws tutorial.

http://observe.ivv.nasa.gov/nasa
/education/reference/orbits/orbits.html

Pictures from Newton's Principia and three user-controllable JAVAscript simulations (one for each of Kepler's Laws) nicely illustrate satellite motion.

Virtual Laboratory, University of Oregon, Eugene, OR.

http://zebu.uoregon.edu/nsf/friction.html

A simulation measuring and describing friction between a block and an inclined plane from the Virtual Lab.