The SDK for Visual Studio 2005 has been released in it’s fourth version, download it here (124 Mb).
The Visual Studio 2005 SDK 4.0 contains a number of new features and fixes, read more about them here.
One of the interesting new features are the Package Load Analyzer which will help you troubleshoot your package load issues. The DSL tools contains a number of minor bugfixes mostly related to the designer.