by Walter Fendt, Augsburg, Germany.

http://home.a-city.
de/walter.fendt/physengl/
springpendulum.htm

Control the mass, spring constant and amplitude of a mass hung on a spring. Displacement, velocity, acceleration force or energy vs time can be plotted in real time. The applet allows you to experiment and determine the relationship between these variables and the period.

Herr Fendt has a collection of other physics applets on his site.

by Professor Mark Sutherland, University of Toronto.

http://thorin.adnc.net/~topquark
/fun/JAVA/dho/dho.html

Control the initial amplitude and damping coefficient for a mass attached to a spring. Displacement, velocity and energy versus time are plotted.

Professor Sutherland has a collection of physics applets and tutorials at fun@learning.physics.