More and more authors are turning to podcasting to find their audiences after being rejected by traditional book publishers, it seems. Interested in hearing some of their stories for free (or if you're feeling generous, a suggested donation of $9.99)? Check out PodioBooks, where there's a tonne of free literature just waiting to be downloaded to your iPod.
Astronomy 161 - an introduction to Solar System Astronomy. These are a set of lectures in progress now at Ohio State University. All materials are available on line - audio resources (direct or podcast through iTunes), movies and lecture notes. If you are interested in where you live, these beautifully delivered lectures are excellent.
Kant. Modern thought begins with Kant yet his work is dense and hard to understand. Perhaps this set of lectures, some 12 hours in total from the University of Glasgow will help. Titled 'Kant's Epistemology' they cover most of the subject matter of the Critique of Pure Reason - an extremely ambitious task. They are free and appear to be available only for a limited period. Perhaps worth downloading now - to savour when you have an few idle years.