The Visual Studio 11 Beta Visualization and Modeling SDK includes

MSBuild tasks that allow to index assemblies as part of a build or from the command line. The code index is used by the Architecture Diagram but can be used on its own as well.
Project templates that help developers create graphical or Form-based (Windows.Forms and WPF) designers hosted in Visual Studio for viewing and editing models for a custom Domain Specific Language.
Project templates that help developers create extensions for the Architecture Tools in Visual Studio 11 Ultimate
MSBuild tasks that allow you to do generate textual artifact at build time for any use of T4
Reference assemblies and IntelliSense documentation for the DSL tools runtime, which ships with Visual Studio 11
A migration tool helping DSL authors who were using the Visual Studio 2010 VsVmSdk SDK to migrate their existing designers to work with Visual Studio 11
Header files containing Command IDs for the graphical designers and the architecture tools (UML designers, Layer designer)
The SDK is not included in the Visual Studio 11 SDK, but does require it to be installed first. The Visualization and Modeling SDK is installed as an overlay of Visual Studio and the VSSDK. It is a separate install so that it can be updated independently