rubular - A ruby based regular expression editor
RegexPlanet Ruby - RegexPlanet offers a free-to-use Regular Expression Test Page to help you check RegEx in Ruby free-of-cost.
RegExr - RegExr.com is an online tool to learn, build, and test Regular Expressions.
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
Regex Widget - Regex Widget is a lightweight, easy-to-use regular expression tester released under the LGPL license.