Jeff Atwood's got a post on regular expressions that included some info on the IgnorePatternWhitespace option which I'd been unaware of till now. That looks like it could be useful.
The comments on his post led to the Regular Expressions Cheat Sheet and to Roy Osherove's Regulazy and Regulator tools. I've used the Regulator in the past but haven't tried Regulazy yet. May want to look into it the next time I'm building a regular expression.