A diagram editor Java applet
This applet allows you to download a diagram from a URL, edit it, and
save it by posting it to a URL. The load/save URLs are given as
arguments to the applet; in this case the save script just writes the
modified diagram back to the original file, so if you modify this
diagram other people will see your changes.
Note that because of Java's security mechanisms it can only load and
save to URLs on the same machine that the applet was loaded from.
The Java source is here.