Dynamical Astronomy JavaLab A variety of interactive Java applets with explanations. Topics include: galaxy interactions, getting the mass of Jupiter from its moons, rotation curve fitting, spacecraft orbits in the solar system, and analyzing galaxy clusters.
Physics Applets (U of Oregon) This set of tools explores various astrophysical concepts via an experimental or observational basis. Most of them are related to spectroscopy and photometry and involve real data sets.