In addition to thousands of hours of experimentation as a hobbyist, hacker, and generally curious child, I have continually studied academic subjects as an adult outside of the academic structure.
I have studied a wide variety of university-level disciplines using resources such as online libraries and archives, YouTube and Google Video, Wikipedia, and full-semester audio/video courses from institutions such as Stanford University and The Teaching Company.
Topics of study have included Earth Sciences and Geology, Classical Physics, Quantum Mechanics, General Relativity, Astronomy, Game Theory, Number Theory, Linguistics, Philosophy, Neuroscience, and iPhone Programming.