There is a nice Eclipse UML plugin "eUML2" from a company called Soyatec. When doing Java stuff I use it for various reasons:
- UML is a good way to communicate designs
- it integrates nicely with the editors (changes in code are reflected in model diagrams and vice versa)
- the file format is XML
- refactorings can also be applied in the diagrams
- the graphic is nicely done and visually appealing
I was suprised to hear that Microsoft is now giving funding to them to develop a Silverlight (yes the one from .NET) integration into Eclipse. See:
Until today support for .NET in Eclipse was very comfortless. There was once a simplified C# Editor and there were no real builders and natures to support compilation for .NET languages. Will see how far they integrate, so new things to try out this evening...