MB Resource Library : Documents Links to other resources
The Application Backwards Compatibility project offers some compilations in a PDF format of changes in the MapBasic language since version 3.0 (look under "Available compilations")
Trey Patillo a reserved a section of his site to some hints and examples of WinAPI32 applications.
Robert Edwards offers on his home.earthlink.net site two sections: the original MapTools SDK with a development kit and several useful tools and the MB_Resource associated site http://home.earthlink.net/~maptoolssdk/
DirectionsMag houses a MapInfo-l section in which one can find a document concerning the MID/MIF format and all the style definitions (look for it in the left pannel)
The original reference to the Windows API library is the Win32.hlp file produced by Microsoft. Each time I need to locate this 12Mo file, I cannot find in on the MS site. I have a copy of it, if you are desesperately in need.
There are several sites dynamizing that file in different ways. One fascinating source is Paul Kuliniewicz's Windows API guide.