Testing regular expressions: RegExhibit and some others

In Mac OS X, you can use regular expressions almost everywhere. Having a good tool for testing your sofisticated regular expressions before the real application is a good idea.

My favorite tool on Mac OS X is RegExhibit (see the screenshot). You may also like Reggy or RegExplorer.  All three programs are free. 
Although simple, they provide basic tools for testing search and replace patterns on a user-supplied sample text.

In the MS Windows world, nothing is better than RegexBuddy (commercial software). However, Expresso (free of charge) is also very good.

Redet looks also very interesting and powerful. Unfortunately, I did not find time to try it, as well as many other tools which are listed here and here...