Microsoft has released the SDK for DirectX 8.1. Thanks Mark.
This “full” DirectX 8.1 SDK download contains the tools needed to build cutting-edge C/C++ and Visual Basic applications. It includes the run-time, headers and libs, sample executables, sample source, documentation, DirectX utilities and support for both C/C++ and Visual Basic development. The “full” SDK download does not include the symbol-file and exporters “extras” downloads. This SDK release also contains the DirectX 8.1 developer runtime and the redistributable runtime.Download