Optimization
Applet
How to find a function's extremum: An applet showing the rectangle of maximum area inscribed in a triangle. [Maths online]
Area of a rectangle applet: An applet showing the rectangle of maximum area inscribed in a semicircle. [Visual calculus]
Cross-section of gutter: Making a gutter which allows the maximum amount of water to pass through. [IES]
The longest ladder: A difficult optimization problem -- getting the longest ladder possible to fit at a right angle. [Visual calculus]
The fastest route: Trying to find the fastest route over the desert. [Visual calculus]
Shortest ladder over a fence: Another optimization problem, this time trying to minimize a ladder but still have it reach over a wall. [Visual calculus]
Online problems
Problems: Several optimization problems worked out in detail, all with very nice animations. [Lane Vosbury]
Problems: Several optimization problems, with detailed solutions. [Duane Kouba]