TextUML Toolkit is an open-source IDE for UML that lets you create models at the same speed you write code. By adopting a textual notation, the TextUML Toolkit provides benefits you will not get elsewhere:
The TextUML Toolkit can be used as a plug-in for the Eclipse IDE, as an independent command-line tool, and as a part of a multi-tenant server-side application - as seen in Cloudfier.
Instructions for installing the TextUML Toolkit. Note you can also use TextUML in Cloudfier, an online IDE and deployment platform for TextUML-based applications.