Visual Studio 2010 SDK Beta 2

The Visual Studio 2010 SDK includes project templates that help developers create tool windows, menu commands, isolated shell projects, and editor extensions. The editor extensions include text adornments, colorizers, and margins.
The Visual Studio 2010 SDK also includes build tasks that help developers build and debug extensions. Building and debugging are managed in a second instance of Visual Studio named the experimental instance. The experimental instance provides a test bed for extensions without changing the primary installation of Visual Studio.
The SDK also puts shortcuts to online documentation, samples, and other developer resources on the Start menu.

Download details: Visual Studio 2010 SDK Beta 2