Computer Architecture

If you don't have a solid mental model of how a computer actually works, all of your higher-level abstraction will be brittle.

Best book: computer systems:A Programmer's perspective

Best video lectures: Berkeley CS 61C

Computer systems

Algorithms and Data structures

If you don't know how to use ubiquitous Data structures like stacks, queues, trees, and graphs, you won't be able to solve challenging problems.

Best book: The Algorithm Design Manual

Best video lecture: Steven Skiena's lectures

How to Solve It as an excellent and unique guide to general problem solving; it’s as applicable to computer science as it is to mathematics.

Math for CS

CS is basically a runaway branch of applied math, so learning math will give you a competitive advantages.

Best book: Mathematics for computer science

Best video lectures: Tom leighton's MIT 6.042J

Operating system

Most of the code you write is run by an operating system, so you should know how those interact.

Best Book: Operating Systems: Three Easy Pieces

Best Video Lecture: Berkeley CS 162

Operating system three easy pieces

Computer Networking

The Internet turned out to be a big deal: understand how it works to unlock its full potential.

Best Book: Computer Networking: A Top-Down Approach

Best video lecture: Stanford CS 144

Computer Networking