http://pinvoke.netThis site is a form of Wiki that developers have contributed definitions of different API calls. Even has declarations for the Cards.dll. It usually provides the VB.NET and C# declarations.
But, there is even more. On the lower left you will see a like "Helpful Tools". This has a listing for a Visual Studio add-in that makes it easy to call up these declarations without ever going to the web site. You can also contribute declarations in the same add-in.
If you ever use the Windows APIs and many COM signatures, this can really help out.
One note: At this time the site is not Mozilla FireFox friendly. You will probably need Internet Explorer to use the site.