I'm starting to use .NET's RegEx class all over...in ways I never expected.  Here's the tools and sites I'm using lately:

• Expresso is a new free tool for working with regular expressions in .NET. [Larkware]
• Of course, RegexDesigner.NET from Chris Sells
• The Regular Expression builder inside of SharpDevelop (which is worth the download just to read the SharpDevelop code!)

And Library Resources:

• RegExLib.com has 213 Regular Expressions at last count (and is hosted by the kick-ass ORCSWeb)
• The Early Adopter Regular Expression Repository at 3Leaf
• The Regular Expression Workbench at GotDotNet.com
• Miloslav's Regular Expression Reference
• Dan Appleman's Regular Expressions with .NET book
• The Tao of Regular Expressions

Outlook2RSS UPDATE: Looks like my Outlook2RSS actually is useful!  Jorge Curioso has built a blog using Outlook2RSS (Which he updated with some Regular Expressions to strip out unwanted tags like HTML and BODY) and ASP.  This is kind of the poor man's inverse of Ingo's Outblog as it's a command-line application that runs as a scheduler task and extracts MailItems or PostItems from Outlook Folders or Public Folders.

Jorge's new blog built on ASP and Outlook2RSS supports these kinds of URLs:

Main Site: http://ocw.abf.tulane.edu/blog/
By Post: http://ocw.abf.tulane.edu/blog/?item=63181048826620
By Date: http://ocw.abf.tulane.edu/blog/?date=2/16/2003

He also points out that this blog is "fully proof-of-concept and prototype in nature."