RegexLord is the IDE for developing regular expression assemblies for .NET. Full stop. It provides syntax highlighting (via the sharpdevelop text editor, http://sharpdevelop.net/), bracket matching, namespace management, code folding, and an easy to
Diagrammer for .Net Assemblies, also support for Javascript. Good for assembly dependencies. Good for showing the call graph in complex methods. Good for showing the jumps in IL. Good for getting an overview of where the complex parts of a system are.