Simple UML diagrams with UMLet

UMLet it's a nice tool for drawing Sequence and Use Cases UML diagrams. It's very simple, intuitive and also funny to use.

My favorite features are the edition of artifacts based in plain text and, mainly, that it's no a pure UML tool, you can draw not fully UML compliant diagrams, and this can be very useful (sometimes)

I think it's a fantastic tool to draw simple and descriptive diagrams rapidly. Of course it's not CASE tool, but also it's cleaner than use a blackboard

UMLet runs as Eclipse plugin, and also as standalone application. Try it!