StarUML is an open source project to develop fast, flexible, extensible, featureful, and freely-available UML/MDA platform running on Win32 platform. The goal of the StarUML project is to build a software modeling tool and also platform that is a compelling replacement of commercial UML tools such as Rational Rose, Together and so on.
我试用一下，速度很快易用性作得不错。帮助文档做得相当好。
启动界面如下：
网址 StarUML