On behalf of the VS Tools Ecosystem team, I am pleased to announce that after months of hard work, VS SDK 4.0 has been released! This is the last SDK release planned for Visual Studio 2005. The team has done a ton of work to make this release friendly to developers who are new to Visual Studio extensibility. It is available for immediate download on the Microsoft Download Center.
Some of the new features included in this release:
There's an article in eWeek for this release. (That's a first for the SDK as far as I know.)