General

• Interactive Mathematics
• Khan Academy

Calculus

• 3Blue1Brown – Calculus Playlist

Linear Algebra

• 3Blue1Brown – Linear Algebra Playlist

Quaternions

• Hamish Todd – GDC: Math in Game Development Summit: A Visual Guide to Quaternions and Dual Quaternions
• 3Blue1Brown – Visualizing Quaternions with Stereographic Projection

Trigonometry

• 3Blue1Brown – Trigonometry Fundamentals
• Khan Academy – Trigonometry Playlist