Visual Studio Integration Program (VSIP)
A small percentage of developers may foray into the tools arena and build extensions for more than the challenge of building cool extensions. Macros, add-ins, and wizards will allow the average developer to build custom extensions to Visual Studio .NET. The fact that these tools exist and are implemented in a purposeful way indicates Microsoft's commitment to encouraging third parties to build extensions to Visual Studio .NET. Then, there is a very small group of vendors that will be intentionally building serious software for Visual Studio. For these folks Microsoft has implemented Visual Studio Integration.
Visual Studio Integration (VSI, also known as VSIP) is a license program that is designed to provide extenders an opportunity to integrate their products into Visual Studio .NET. For more information, refer to the "Visual Studio Integration Technical Guide" available from Microsoft.
To be brief, participating in this program costs a small chunk of change, and for your participation you get a Visual Studio Integration SDK and Visual Studio for Applications among other perquisites. Visual Studio for Applications itself is a pretty nifty product for writing custom extensions to applications without modifying the source code.
If you are an extendercompanies like Turbo Power, Rational Software, Starbase, and IBM come to mindyou will want to look into the VSIP program.