Regexper: Beautiful regexp visualizations
Pretty neat, although I have a nitpick with your choice of a block labeled "None of:" in for example this regex: /foo(.*)[^0-9]+bar/<p>It ends up saying "none of [0-9]" when that's not actually a good english description of what should go there.  It should say something equivalent to "one or more things that are not [0-9]".  The empty string fits the description "none of [0-9]" but does not match that part of the regex.