It's OK to shamelessly plug yourself if you're introspective about it.  That's what I always say.  Roy posted Regulator and it is quite the studly Regular Expressions IDE.  A good addition to anyone's C:/UTILS.  With all these RegEx tools, I'm all set:

• Roy Osherove's Regulator - Roy enters the RegEx fray with a bang, and with syntax highlighting and web services integration with regexlib.com. The very definition of slick.
• Eric Gunnerson's Regular Expression Workbench - Nice .NET interactive Regular Expression builder.
• Expresso is a new free tool for working with regular expressions in .NET.
• RegexDesigner.NET from Chris Sells
• The Regular Expression builder inside of SharpDevelop (which is worth the download just to read the SharpDevelop code!)

Regulate - Warren G
I'm tweaking
into a whole new era
G-Funk
step to this
I dare ya
Funk
on a whole new level