The VS team recently released an update of the MPFProj sample sources to facilitate authoring custom project types for Visual Studio 2012. Including a link to each version below; as each is specific to a given version of the Visual Studio IDE.
Samples that leverage the MPFProj sources:
Note, the original MPFProj sources were first included in the Visual Studio SDK for VS 2008. And while it’s a bit dated, the IronPython Integration Deep Dive whitepaper is a good write up of the sample, including details on implementing the project system.