Generally the lectures are roughly an hour to an hour and a half. Part of that is question and answer – believe it or not the Q&A is generally almost as worthwhile as the actual subject. I’d get fidgety if I had to sit that long, but since I’m listening at my leisure I can do other tasks, pause the lecture, etc.
There’s a lot of variety in the subject matter of lectures. International studies. History. Literature. (I’m downloading a poetry reading by Yevgeny Yevtushenko next time I haul my computer to an wireless access point.) The ill effects of the corporatization of universities and colleges. (Speaking of my college...) Film studies. Queer theory. Human Rights. Etc., etc., and so on and so forth. I don’t listen to every lecture, because I’m only passingly interested in some topics, but there’s plenty of material to choose from.
So, highly recommended for listening material.