RegEx Editor
This sample was built to ease your pain when working with regular
expressions. It rehosts the editor in a dialog box and provides a basic
language service to provide colorization, brace matching, sample
testing grouping and selection tracking. It shows re-hosting of the
editor in a tool window, and provides a nice starting point for similar
projects.

To try this extension install Visual Studio 2010 and then download with the download button at the top of this page.
To see the code for this extensio.