• MSDN Online library
  Everything you wanted to know about MS Windows, including full API documentation
• 
  The Netwide Assembler - a powerful, portable, and free Intel x86 assembler. Use with ALINK to write Windows 95/NT and MSDOS programs
• WDOSX DOS extender
  Create 32-bit MSDOS applications using ALINK and WDOSX
• P32
  A 32-bit Pascal compiler
• PPro
  Another 32-bit Pascal compiler
• Mingw32
  GCC port for win32
• RSXNT
  GCC port for MSDOS/Win32
• 
  Source code, utilities and links
• The Free Country
  More Source code, utilities and links
• Jeremy Gordon's Win32 + Assembler Source Page
  Jeremy Gordon has written a brilliant Free Resource Compiler (goRC), which you can download from here
• HexIt! Home Page
  HexIt is a great windows hex editor

Books

• The C++ Programming Language, Bjarne Stroustrup
  The definitive reference guide to C++.
  Buy it at amazon.com or amazon.co.uk
• The C++ Programming Language, Special Edition, Bjarne Stroustrup
  The special edition of the above, with extra appendices
  Buy it at amazon.com or amazon.co.uk
• The Annotated C++ Reference Manual, Margaret Ellis and Bjarne Stroustrup
  Buy it at amazon.com or amazon.co.uk