Tachy is a Scheme-like (R5RS is the template, but not the goal) language that is being developed in C# for the .NET framework and is made available as Open Source (BSD License). The current implementation is an interpreter, and a compiler is planned. The primary focus for Tachy is for programming language learning & experimentation, and an attempt has been made to keep the code as small(currently under 1000 lines) and straightforward as possible.
(via StackOverflow)