Resource types:

• free website
• free website, registration required
• paid website
• free book/ebook
• paid book/ebook
• Open Access Journal

• Feynman Lectures on Physics (Audio Recordings)
• Feynman Lectures on Physics Course Handouts  (Richard Feynman, California Institute of Technology)
• Feynman's Tips on Physics  (Richard Feynman, California Institute of Technology)
  How to solve problems in physics
• Flipping Physics
• HyperPhysics  (C.R. Nave, Georgia State University)

• Classical Physics (Lectures)  (Professor Dave)
• Classical Physics (practice problems)  (Professor Dave)
• Classical Physics Practice Problems  (Professor Dave)
• Crash Course Physics  (Shini Somara)
• Introduction to Classical Physics  (Professor Dave)
• MIT Physics I (8.01x) - Classical Mechanics  (Walter Lewin, Massachusetts Institute of Technology)
• Optics (2.71, 2014)  (Nicholas X. Fang, Massachusetts Institute of Technology)
• Physics with Professor Matt Anderson  (Matt Anderson, San Diego State University)
  comprehensive course for introductory university physics
• The Feynman Lectures on Physics, Volume I  (Richard Feynman, California Institute of Technology)
  Mechanics, Radiation, and Heat
• The Feynman Lectures on Physics, Volume II  (Richard Feynman, California Institute of Technology)
  Electromagnetism and Matter
• The Physics Classroom

• Waves & Electromagnetism  (Aerostudents, TUDelft)

• Modern Physics (Quantum Physics)  (Professor Dave)
• The Feynman Lectures on Physics, Volume III  (Richard Feynman, California Institute of Technology)
  Quantum Mechanics

• Plasma Physics and Applications  (M. V. Sunil Krishna, Indian Institute of Technology Roorkee)