If you found this site you are probably already familiar with the Javadoc Tool provided by Sun Microsystems and the documentation for the Javadoc Technology released with every JDK.
The Javadoc Plugin uses the Javadoc tool to generate Javadocs for the specified project.
Sun also provides an experimental Doc Check Doclet that reviews documentation comments. There is a Maven plugin called maven-doccheck that provides a doccheck report for Maven 1 and also presents instructions to generate a doccheck report with Maven 2.