A coworker of mine has been working on a ajax enabled regex tool which lets you evaluate regex expressions in several languages (including PHP PCRE and PHP POSIX) with instant results. You can choose which functions to use, such as match, match all, replace, split etc. It also offers some basic help and hints. It’s really handy when working on those painful expressions.

You can check it out at http://regex.larsolavtorvik.com/. Stop by his blog as well.