The Game of Sprouts at University of Utah, with an interactive applet for human-vs-human play.

An interactive applet showing several triangle centers that lies on the Euler line.

Angle definition pages with interactive applets that are also useful in a classroom setting.

Math Open Reference Shows three different ways to compute the area of a rhombus, with interactive applet.

Angle definition pages with interactive applets.

The interactive applet conveys a good intuition of the idea behind the formal proof.

How to Draw a Straight Line, online video clips of linkages with interactive applets.

Goproblems.com site has over 3000 life and death and other Go puzzles, in an interactive applet.

World of Polyhedra - metabigyrate rhombicosidodecahedron (interactive rotatable wireframe applet)

The application supported personal course histories, personal notes to content, automatic tests and interactive cooperative applets for teamwork in lessons.