Irony is a framework created by Roman Ivantsov and used to write internal DSLs or entire new languages that run on .NET, the grammar being written in C#.
Irony, a CodePlex project, allows one to create a new language by specifying its grammar directly in C#. The framework generates the scanner and the parser making the job of creating a new compiler considerably easier. The project contains a JSON sample implementation:
The project contains several other sample grammars like C#, SQL, Scheme, Script.NET, GwBasic, Ruby, and Python. It includes a visual grammar explorer.
Irony is currently in Alpha released under the MIT License (MIT). It requires VS 2008 and .NET #.5.
Resources: Irony on CodePlex, Expression Grammar Sample, Writing a VS Language Service with Irony.