UMLet Free UML Tool for Fast UML Diagrams

UMLet is a free, open-source UML tool with a simple user interface: draw UML diagrams fast, buildsequence and activity diagrams from plain text, 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.