Write Your Own Operating System

lowlevel.eu (german)
Jonas Berlin VGA initialization
Chris Giese VGA initialization
C++ Reference (best I know - I use it all the time)
gnu.org tutorial on inline assembler

Graphics File Format Specifications

Great Keynote Speech by Bjarne Stroustrup about memory management
Another Great Speech by Bjarne Stroustrup
Great Talk by Bob Martin about Object Oriented Programming (really starts at 12:30)
Great Tutorial on Exceptions in C++
Don't Help the Compiler
Great Tutorial on OpenGL
In-Depth Tutorial on git
Impressum, Datenschutzerklärung etc. W3C Validation