Microsoft offering the visualization and modeling software development kit for Visual Studio 2010 via its MSDN Code Gallery. According to Redmond company, the MSDN Code Gallery is now the official home for all Microsoft Visual Studio Visualization and Modeling SDK online resources. Here, you'll find samples for DSL Tools, for Architecture tools extensibliity, you find deep dive documentation, and get links to shared source projects and other resources to help you create Graphical and Form-based Modeling Designers for VS with the DSL Tools and architecture tools. Note that VSVMSDK is the successor of DSL SDK (also named DSL Tools). It now includes some content enabling the extensibility of Architecture tools of Ultimate edition of Visual Studio 2010.
All DSL Tools related resources on Code Gallery are tagged with "DslTools" tag.
More Info: VSVMSDK