Recently, I discovered that church historian Carl Trueman had lectures on the Reformation available to be downloaded. I promptly acquired these lectures and put them on my phone. Over the course of a few weeks, I was able to listen to all of them while walking, driving in the car, and even while playing some old video games from my childhood. Trueman's lectures are some of the best that I've ever listened to on the Reformation. His blending of facts and his distinctly British sense of humor make them a fun and easy listening experience.
You can download this great course from iTunes U. The course is also available on the Westminster Theological Seminary website to listen to or download.