Richard Feynman was obviously famous for his work as a physicist, but he's also widely regarded as one of the most lucid and effective lecturers to ever address an audience. So renowned, so readily accessible were his presentations, that his introductory physics lectures (which he delivered to undergraduates at Caltech) have since been immortalized in the form of a three-volume set called, quite simply, The Feynman Lectures.
The set is a phenomenal resource to anyone with even a passing interest in the physical world and the laws that govern it — but even these lectures cannot capture the essence of what it might have been like to attend a presentation given by Feynman himself.
Fortunately for all of us, in 1964, Feynman delivered a series of seven hour-long lectures at Cornell University. Those lectures were recorded by the BBC, and in 2009 (with a little help from Bill Gates), they were released to the public. You'll find all seven of them featured below, but you'll also want to check out the lectures on Microsoft's Project Tuva, where they have been carefully edited to include closed captioning and annotations.
Lecture 1: Law of Gravitation — An Example of Physical Law
Lecture 2: The Relation of Mathematics and Physics
Lecture 3: The Great Conservation Principles
Lecture 4: Symmetry in Physical Law
Lecture 5: The Distinction of Past and Future
Lecture 6: Probability and Uncertainty — The Quantum Mechanical View of Nature
Lecture 7: Seeking New Laws