A massive amount of notes and links about unreal, c++, and many other languages and technologies. The unreal notes doc was a good first read when starting to dip past the surface of the engine.

Orfeas’s site is another gold bookmark with many unique c++ tutorials for Unreal, covering some uncommonly found topics.

One of the most important Unreal C++ learning sites around. Tom’s work can teach you everything you need to know about Unreal.

Formerly benui.ca — a learning site with a huge number of great Unreal tutorials and resources, mostly focused on UI, but covering a variety of topics in the engine.