RazorPad is a quick and simple stand-alone editing environment that allows anyone (even non-developers) to author Razor templates. It is the Notepad for Razor.
The application is developed in WPF using C# and relies on the System.WebPages.Razor libraries (included in the project download).
NOTE: This is Alpha stuff. I can only say that it works with basic scenarios, and even then I'm not responsible for anything that goes wrong...