UMLet

Open Source / Non-Proprietary

a Java-based UML tool (licensed under the GNU GPL)

NEW: UMLet 9.03
Free UML Tool for Fast UML Diagrams
UMLet is an open-source UML tool with a simple user interface: draw UML diagrams fast, export diagrams to eps, pdf, jpg, svg, and clipboard, share diagrams using Eclipse, and create new, custom UML elements.

UMLet runs stand-alone or as Eclipse plug-in on Windows, OS X and Linux.

New in UMLet version 9: improved and leaner GUI; better custom element support; easier start-up; better Eclipse integration; improved exports to eps and clipboard ... New in UMLet version 8: fast activity diagram creation with text-based syntax; variable font size; better crop when exporting graph to clipboard...

http://www.umlet.com/