T4 Templates are found in the various software factories and DSL Tools shipped by Microsoft Patterns & Practices. A Visual Studio T4 Editor has been developed by Clarius Consulting that works within Visual Studio to provide statement completion and a better experience from within Visual Studio when editing T4 Templates.
Some interesting facts mentioned by the T4 Editor Website:
"The Text Templating Transformation Toolkit (better known as T4) is a text transformation technology developed by Microsoft and used mostly for code generation by products like Microsoft DSL Tools.
The T4 engine used to support transformations is currently distributed by the Visual Studio SDK and with the advent of Visual Studio 2008 (codenamed Orcas) the T4 bits will be come pre-installed "into the box" on all Visual Studio installations (Standard edition and better)."
Very cool. Learn more here.