RegexBuddy - RegexBuddy is your perfect companion for working with regular expressions.
rubular - A ruby based regular expression editor
Patterns - Patterns is a simple yet powerful tool for working with regular expressions.
RegExr - RegExr.com is an online tool to learn, build, and test Regular Expressions.
Expressions - An app to play with regular expressions. Easily and nicely.
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.