DWM Managed API
Desktop Window Manager was introduced with Windows Vista and it enables the Aero GUI. The library that exposes the DWM functionality is dwmapi.dll. A while ago, I wrote a C# wrapper over the library to enable WinForms applications to use the new user interface capabilities. The DWM Managed API covers most of the DWM functionality, except the frame timing API (which most developers shouldn’t need anyway).
Feel free to download, use, modify and extend it.
You can find more information on DWM (the Win32 API) here: http://msdn.microsoft.com/en-us/library/aa969540(VS.85).aspx