Digital Design and Computer Architecture recommended by Vipul Vaibhav
Computer Architecture course recommended by Abhinav Upadhyay
Art of 64-bit Assembly: Recommended in FFmpeg assembly programming course
Operating Systems: Three easy pieces
What every developer should know about Concurrency: Abhinav Upadhyay
Advanced programming in the Unix environment
Beej's Guide to Network Programming
Mike Acton's famous Data-Oriented-Design talk