IronMeta is an implementation of Alessandro Warth's OMeta metaprogramming system in C#. It provides a packrat parser generator that generates parsers for Parsing Expression Grammars that operate on arbitrary streams of objects.
A simple way to create a syntax highlighting editor for a custom language/grammar and/or create custom grammar parsers. This is a .NET project written in C#. See details here: http://acct001.com/wordpress/?p=190