Yesterday, version four of the Visual Studio 2005 SDK was released. While I don't plan on developing any Visual Studio add-ins or extensions, I noticed that the SDK included SandCastle, which is a tool to build documentation based on your inline XML comments. If you're working with large or distant groups, it can help to compile some of your work into a readable API document, and SandCastle will do that for you. You'll need to go to http://www.sandcastledocs.com/ to get an automation script or GUI, since this release doesn't include any interface.
While I was poking around Microsoft Download Center, I noticed two other interesting downloads. The first is the Consolas Font Pack for Microsoft Visual Studio 2005. This is just a new "optimized" font for programming, which will automatically install itself as the default font for VS2005. I think it looks pretty slick.
Lastly, the Microsoft Visual Studio 2005 IDE Enhancements are a group of power toys including a Diff utility and Source Code Outliner. I haven't had a chance to check them out fully, but a couple of them look like they might be useful.