In 2006, pianist András Schiff gave a series of eight lecture-recitals covering the complete cycle of Beethoven piano sonatas. Here are all the lectures on one page. (Beware: The metadata on these mp3 files is all over the map.)
As an incompetent student of the Beethoven sonatas, I find these lectures absolutely riveting.
Note: Schiff assumes you are familiar with basic musical terminology, terms like exposition, subdominant, Neapolitan, enharmonic and quaver.