Piotr Gawrysiak's Alpha VRML Plot uses Javascript in conjunction with Virtual Reality Markup Language to create 3D plots of equations specified by the user. The script requires Netscape 3 or higher with VRML viewer plug-in. Some knowledge of JavaScript is required to specify the equations. Marcus Kazmierczak's Simultaneous Equation Solver solves three simultaneous equations given coefficients entered by the user. The Danish Wind Turbine Manufacturers Association's Wind Energy Economics Calculator is a large Javascript form which calculates the economic benefits from investment in a wind turbine, given parameters that can be changed by the user.
Extensive help is available by clicking on the question marks.
Kim Sosin's Exercises on Supply and Demand use Javascript to implement a test and to animate a graph to illustrate the correct answer. Brian Tissue offers some JavaScript functions for making multiple-choice questions. These are free for non-commercial use and can be easily adapted by pasting text into the scripts. Netscape JavaScript Resources including examples, tutorials and links.