Languages

C++

cppfaq

Marshall Cline’s cppfaq

C++11

The book "Effective Modern C++" by Scott Meyers is a must-have.

STL

Tricks/Gotchas/Hacks

Go

Algorithms and Data Structures

Design

OOAD and principles

Data Oriented Design

Operating Systems

Linux

Multi-threading, Concurrency

One of the book on the topic is "The Art of Multiprocessor Programming" by Maurice Herlihy and Nir Shavit

Architecture