A nice gem built by Roy Osherove:
Regex Debug Visualizers for Visual Studio 2005
Visual Studio allows creating "Debug Visualizers" for all types in .NET framework as well as custom types.
You can find such visualizers for Datasets, strings and XML. There wasn't one for Regular expressions, until now. These visualizers allow you to "visualize" the following types:
System.String
System.Text.RegularExpressions.Regex
System.Text.RegularExpressions.Match
System.Text.RegularExpressions.MatchCollection
Very cool use of Visualizers, Roy!
Get it here.