From the download overview: "This is the official Visual Studio 2005 software development kit that allows developers to integrate tools, editors, designers, languages, and much more inside Visual Studio 2005. It adds the following features: VS SDK Browser, Package Load Analyzer, Toolbox Control Installer together with a toolbox control installation sample, a redistributable package for Toolbox component vendors that simplifies deployment, a new tool for generating managed class library documentation (Sandcastle), an updated Setup experience, a new toolbar combo box sample, new integration tests for the EditorWithToolbox sample that use the VsIdeHostAdapter and much more."
Go check it out, and please let us know if you have any troubles using it by sending mail to vssdkfbk AT microsoft.com. Also note that this release requires Visual Studio 2005 SP1. I will be blogging more about some of the new features in the release over the next several days.
This release of the Visual Studio 2005 SDK is the final one which will target Visual Studio 2005. As Visual Studio Codename Orcas approaches Beta now, the Visual Studio SDK team will be shifting our focus to providing new samples and tools targeting the new features in Visual Studio Codename Orcas. Speaking of Orcas, the March 2007 CTP has also just shipped.