Larry pointed me towards some of the Pirol plug-ins for OpenJUMP today. I don't think the Pirol project is heavily involved in OpenJUMP programming any more, but you can still get their plug-ins online. All of the plug-ins appear to be released under the GPL, and the source code is included with the JAR file downloads. You can get these plug-ins for OpenJUMP here:
Most of the page is in German?/French? but there are short English descriptions of each plug-in.
Some of these plug-ins look quite useful, and I may start to host the source code and executable form of these plug-ins at the SurveyOS Project.
The Sunburned Surveyor