George Reisman offers a free introduction to his theory of profit/interest and its major applications: an integration of the classical school's notion of profit with the Austrian idea of original interest.
(The file is a 29 megabyte Adobe pdf file, with each page accompanied by oral commentary. You will need a special Adobe plug-in, here is a download for Adobe 7.0 including the necessary plug-in.)
Reisman is the author of the book Capitalism, his magnum opus, available free on pdf at his site. Larry Sechrest has described it as "probably the most remarkable textbook written by any economist in this century. It is a book that will broaden the horizons of economics students at the same time that it challenges and provokes their professors. It is, quite simply, must reading for anyone interested in economics." This oral presentation offers a good introduction.
Linked presentation here.