Sorry, you need a Java-enabled browser to see the simulation.
This java applet is a simulation that demonstrates standing waves on a vibrating string (a loaded string, to be precise).

To set the string in motion, click "Center Pluck" or "Fundamental", or click on the string.

Below the string you will see a graph showing each normal mode's contribution to the string's vibration. There are two sets of bars; on top are the magnitude bars, which shows the amplitude of each normal mode. These bars can be adjusted with the mouse, or you could double-click on one to isolate a particular mode.

This applet has sound if you are using java 2. If you don't see a "Sound" checkbox, then you should get the Java plug-in.

Full Directions.

Zip archive of this applet.

Rectangular membrane applet.

Bar waves applet.

More applets.

The source.

Version 1.5a, posted 4/2/14