I'm a man of simple needs...especially when it comes to Regular Expression building tools. Roy Osherove has made an excellent tool in The Regulator - however, for my needs it's a bit too complicated for daily use, undoubtedly powerful but just a bit complex. For me, Expresso by Jim Hollenhorst is just perfect, lets me build and test regular expressions in a compact environment with nothing that I don't need. Anyway, try it out!