I am always looking for new and interesting podcast to listen to as I ride to bus to and from work. I generally focus on science and nature podcasts, although I do mix in other flavors every now and then. Some of my long standing favorites include NPR Science Friday, BirdNote, KBSU: Off the Trail, Stratfor Daily Podcast, and This Week in Science.
I was recently searching for some interesting content in biology or ecology. I've tried a few but haven't found the right content yet. During my search I came across the Earth and Environmental Systems podcast. While not exactly what I was looking for this is an excellent program. The creator is a professor at Colorado School of Mines and the content is based upon one of his courses. Each program is about an hour in length and covers a particular theme. The series began with geology, moved into hydrology, then weather and climate, into life, evolution, ecology, and biodiversity. The program continues but that is as far as I have gotten. It covers a great deal of information. I highly recommend it.