I know some people will say WHAT? but I think understanding the history of programming languages is interesting. When I have free time, I like to listen to scientific books in physics, math, and chemistry. I was shocked how powerful this method. You'll be able to understand the root of the problem not only that you will also be able to use the technique properly because you got the idea. Unfortunately, I didn't find any audio book about the history of programming languages or at least any good documentary. Have you came across of any audio or well documentary?
When you have free time you like to listen to scientific books? o.O I must be old because I prefer to actually read those kind of books :P. Though, documentaries are normally biased or leave out details.