From Ten Dollar Dev Tools:
Enter any source text and any regular expression text. Validate your work as you type since the results are computed in real-time. Handy scraps panel allows to to insert common, predefined Regex snippets. Add your own custom scraps for Regex snippets you don't want to forget. When your Regex is just right, you can copy and paste the automatically-generated C# or Visual Basic code into your code editor. Great timesaver whenever you need to create a new XSL transform, update an existing one, or simply verify it works as expected.