http://www.jgraph.com/jgraphpad.html
This is a Java-based powerful, free diagram editor that allows you to create flow charts, maps, UML diagrams, and more.
You can find the download on SourceForge.
http://sourceforge.net/project/showfiles.php?group_id=43118&package_id=65494
Source: OS/2 Warp News and Rumors