Related rates
Applets
Related rates applet: An applet showing how a person's shadow changes as they move near or from a lightsource. [Dartmouth]
Related rates applet: Mess around with two ships in a near (or not-so-near) collision. [U.S. Navy]
Online problems
Problems: Several related rates problems worked out, all with nice animations to illustrate the situation. [Lane Vosbury]