There have been some pretty interesting open-source/shared-source projects going on out there. Thought I would put a small list of those:
Gyro
Gyro is a set of files that convert an existing installation of the Microsoft Shared Source CLI to support generic type definitions and generic methods. These generic constructs take types as parameters, and are primarily intended to better support typed containers such as lists, stacks, and dictionaries.
http://gyro.sscli.net
Compiler Generation Tools for C#
Coco/R is a compiler generator which in its current version takes a compiler description in the form of an attributed, context-free EBNF grammar (ATG) and generates the corresponding scanner and recursive descent parser.
http://dotnet.jku.at/Projects/Rotor/
Distributed Virtual Machines: Inside the Rotor CLI
The Common Language Infrastructure (CLI) is a multiple language runtime system, first implemented as the .NET Common Language Runtime (CLR). In March, 2002 Microsoft released the Shared Source CLI implementation (aka Rotor) for general educational use. The CLI technology can be used to address a spectrum of software design and development barriers that cut across compilers, runtime systems, and operating systems. This book focuses on the parts of the technology that are directly related to distributed virtual machine technology. It covers assembly architecture, assembly loading, downloading, the execution engine, security, CLI inter-object communication (remoting), and more.
http://wps.aw.com/aw_nutt_dvm_1/
Research Projects Using the Shared Source CLI
http://research.microsoft.com/programs/europe/rotor/
Windows Template Library Shared Source Licensing Program
The Windows Template Library (WTL) helps C++ developers build lightweight graphical user interface (GUI)-style applications for Windows. Functionally, WTL is a light-weight windowing template library for C++ that provides support for many Windows user interface elements.
http://www.microsoft.com/resources/sharedsource/Licensing/WTL.mspx
STL.NET Primer
With Visual C++ 2005, the Standard Template Library (STL) has been re-engineered to work under the .NET Framework. This article provides a general tour of STL.NET.
http://msdn.microsoft.com/library/en-us/dnvs05/html/stl-netprimer.asp