I was recently looking for a simple and lightweight UML2 Design Tool and came across RedKoda which does exactly what is required for most cases which is draw diagrams in a fast and easy way. It is the simplest tool I have ever seen on UML2 Design and only 500kb in size!!
The supported diagrams are the following :
-Class diagrams, component diagrams, composition structure diagrams, deployment diagrams, object diagrams, package diagrams
– Activity diagrams, use case diagrams, state machine diagrams
– Communication diagrams, interaction overview diagrams, sequence diagrams, timing diagrams
Why don’t you download and give it a try @ http://www.redkoda.com