One of the podcasts I listen to regularly is The Long Now Foundation’s Seminars About Long-Term Thinking. Each episode usually features a one-hour lecture by a guest speaker, followed by half an hour of questions from the audience. Topics and speakers vary a great deal, but the common theme of the series (and of the foundation itself) is to promote thinking and planning over the long term—decades or longer. Besides the obvious historians and futurists, speakers also include artists, politicians, and all kinds of scientists. Some examples are Ray Kurzweil on the future of technology, Jimmy Wales on Wikipedia and free culture, Vernor Vinge on the singularity, and Craig Venter on trawling the ocean for DNA.
There’s been about one lecture a month since the series started in 2003, and the whole back catalog is still available. It took me quite a while to get through it, but it was well worth the time—and, true to their subject, the lectures age well and stay relevant.