MoXAML Power Toys is a Visual Studio AddIn that’s designed to make your coding that bit more productive for WPF/Silverlight applications.
Designed to be easy to add your own plug ins to, MoXAML provides a central repository for managing tasks such as prettifying XAML files, managining multiple XAML code comments, automatically adding field modifiers and so on. All source code is present here - there's no hidden voodoo, and no hidden files. It's all available for you to use, and to extend as you see fit.
More details can be found on my blog at http://peteohanlon.wordpress.com/moxaml-power-toys/