YouTube - 3Blue1Brown - Calculus and Linear Algebra - Animations for Mathematics Concepts (Gives Visual Intuition)
YouTube - Art of Problem Solving - Creative Math Problem Solving
YouTube - Cyclic Squares - Creative Math Problem Solving
YouTube - LetsSolveMathProblems - Creative Math Problem Solving
YouTube - Matt Superdock - Creative Math Problem Solving - Takes AMC 10/12 and AIME I/II "live" (tests timed).
YouTube - Walt S - Creative Math Problem Solving
Updated as of June 15th, 2018