The "Bible" of Windows API programming:
"Programming Windows", Fifth Edition by Charles Petzold.
The book was originally written and published for Win9X, so not every code example will compile without some modifications.
The code examples have been updated and put into a gitub repo.
There is a 6th edition of "Programming Windows," but it uses C# and is targeted for Win 8.
There a similar book for MFC programming: "Programming Windows with MFC", Second Edition by Jeff Prosise.
As I said, neither book is recent, but they still do a good job of showing the nitty-gritty of bashing together code for low-level Win programming.
There really is no "one stop shopping" online when it comes to tutorials and example code for learning Win32 technology anymore. Examples are flung far and wide in tidbits here and there.
theForger's Win32 API Tutorial is still available. It is a bare-bones beginners look at the Win32 API.
Fair warning: the code was written back in Win9X days, the Win32 API has changed since then. I have a github repo where I updated the code to better reflect modern Win API coding practices.
Two more WinAPI tutorials.
A tutorial for MFC, though I can't say it if it good or not. I've only skimmed the contents.
Older versions of the WinAPI SDK were available for download, and included example sample code along with the Win SDK documentation accessible offline. I believe it is still possible to download the archives, though I haven't looked for any for years.
MS has git repositories for Windows API sample code online, though the samples are coded to use the WinRT and C++. The original WinAPI was C based.
MS documentation for the WinAPI is all online now. Hard to follow and get an overview of what's available IMO.
There's a lot of 3rd party code available out on the interwebz for C-based WinAPI and MFC still.
Microsoft as a github repo of a lot of "classic" code examples for Windows Desktop apps.