The internet is just loaded with ways to fill your iPod with smart stuff for free!
The best site for free audio smart stuff is LibriVox. This is a sister project to Project Gutenberg their mission is to supply mp3s of people reading books, articles and stories in the public domain. I have found the quality of the readers to be uneven, but I can’t complain because it’s all free.
Even though it is incomplete, if you want some free Shakespeare audio students at Los Medanos college have a podcast where they are working their way through all of Shakespeare’s work. What they have done already is available on their site. Shakespearecast.
Finally, Stanford University offers free audio of faculty lectures on many different topics. This is an amazing service. They have three courses that they are offering all lectures completely free of charge.