JGraph is the most powerful, lightweight, feature-rich, and thoroughly documented open-source graph component available for Java. See the project homepage at www.jgraph.com for information and downloads.
ahahaha. Just love the review below. A DLL for a Java Swing product? And you were trying to buy a free product from a salesman? Totally unfair to question your competence there... Classic :D.
Wonderful component. Easy to use yet very powerful.