This paper describes a Flash-based OSSLET that we have used at the United States Military Academy with first year calculus students as a vehicle for motivating vectors, matrices, and linear and affine transformations.
This site includes two applets, one for visualizing the approximation of a square wave by trigonometric series, and the other for hearing successive approximations to the displacement curve of a sound wave.
This Java applet allows the user to experiment with Riemann sums. It can also be used to approximate definite integrals or find upper and lower bounds to the exact value of a definite integral, using Riemann sums.
This utility uses the free Flash player plug-in resident in most browsers to allow the user to plot parametrically defined surfaces in spherical coordinates. Many examples and directed exercises are included.