RegExr - RegExr.com is an online tool to learn, build, and test Regular Expressions.

rubular - A ruby based regular expression editor

Expresso - The award-winning Expresso editor is equally suitable as a teaching tool for the beginning user of regular expressions or as a full-featured development environment for the experienced programmer with an extensive knowledge of regular expressions.

RegexPlanet Ruby - RegexPlanet offers a free-to-use Regular Expression Test Page to help you check RegEx in Ruby free-of-cost.

RegEx Generator - RegEx Generator is a simple-to-use application that comes with the brilliance of intuitive regex and is also helping you out to test the regex.

Reggy - Signup forms filled automatically with random identities