RegexBuddy - RegexBuddy is your perfect companion for working with regular expressions.
Expressions - An app to play with regular expressions. Easily and nicely.
RegexMagic - Use RegexMagic to generate complete regular expressions to your specifications by using RegexMagic's flexible patterns, instead of the cryptic regex syntax.
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.
rubular - A ruby based regular expression editor