Here's a few of the places that I have found for information and picked up some strings that are included here.
Using Computers in Linguistics: A Practical Guide
A.K.A. UNIX for Linguists, this page has an interesting perspective on Regex, essentially considering it mathematics for language. A few good links and some text. Not very in-depth, unless you're into Regex's place in the the Chomsky Hierarchy.
Jeffrey E. F. Friedl
Jeffrey is the Winston Churchill of the Regex community, having written the first book dedicated solely to exploring the power of Regular Expressions. This page is the only one that I could find that was still active. Jeffry, if you read this, please let me know where you're moving your page to.
Programming Perl, Chapter 1, Section 7
This exerpt from the Camel Book covers the use of Regex in Perl. Thanks to O'Reilly, we can access this first chapter on the web for free, though any true Perl user will pick up this book just to support Larry Wall and O'Reilly so that Larry can continue working on Perl.
This program was developed to clean up the odd markup that Microsoft products produce with their 'Save as HTML' options. I havent used it, but the regex pieces were quite sound. :)