Stanford University is offering audio versions of leactures and talks online for free. They cover quite a range of topics so most people should find something interesting there. Unfortunately they're offering it through iTunes fortunately seeing they're free you don't need an account to access them. Any way have a look here if your interested Stanford iTunes.
The lectures Range from Nature Sustainability, Global warming, to religion and political science, there is also some classical music and other related materials there.
Have a look and download a few if they look interesting.