Leonard Susskind had recorded many video lectures across many branches of physics and all of can be found on this official website. Pdf versions of three of the video courses (taken and shared by some generous person) are available in the following links to download for free
There also exist three textbooks by Susskind based on these videos lectures (and I own all of them)
More can be found here and here. Hope I didn't miss any. But he has given many other supplemental courses as well such as Quantum Entanglement, Particle Physics 1: Basic Concepts, Particle Physics 2: Standard Model, Particle Physics 3: Supersymmetry and Grand Unification, String Theory, Cosmology and Black Holes etc. But unfortunately, I could not find the PDF notes of any of these supplemental courses on the Internet. Does anyone have the PDF notes of these lectures? Please share the link if available. Thanks!