CodeRush - DevExpress CodeRush for Roslyn uses significantly less memory, works faster, and lets you start Visual Studio faster.
rubular - A ruby based regular expression editor
Visual Assist X - Visual Assist X dramatically reduces application development time with key new features and...
RegExr - RegExr.com is an online tool to learn, build, and test Regular Expressions.
ReSharper - ReSharper is a productivity tool for visual studio that provides tools and features to help you manage your code.
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.