PlantUmlEditor is my new free open source UML designer project built using WPF and .NET 3.5. If you have used plantuml before, you know that you can quickly create sophisitcated UML diagrams without struggling with a designer. Especially those who use Visio to draw UML diagrams (God forbid!), you will be at heaven. This is a super fast way to get your diagrams up and ready for show. You can *write* UML diagrams in plain English, following a simple syntax and get diagrams generated on-the-fly.
This editor really saves time designing UML diagrams. I have to produce quick diagrams to convey ideas quickly to Architects, Designers and Developers everyday. So, I use this tool to write some quick diagrams at the speed of coding, and the diagrams get generated on the fly. Instead of writing a long mail explaining some complex operation or some business process in English, I can quickly write it in the editor in almost plain English, and get a nice looking activity/sequence diagram generated instantly. Making major changes is also as easy as doing search-replace and copy-pasting blocks here and there. You don't get such agility in any conventional mouse-based UML designers.
I have submited a full codeproject article to give you a detail walkthrough how I have built this. Please read this article and vote for me if you like it.
PlantUML Editor: A fast and simple UML editor using WPF
You can download the project from here: