This is an incredible resource. Founded in 1940, the Chicago Civil War Round Table has made available audio recordings of presentations going back to 1951. You can listen to Bell Wiley, T. Harry Williams, Bruce Catton, Grady McWhiney, Alan Nolan, Douglas Southall Freeman, and others discuss a wide range of topics.
It also offers a window into how the field of Civil War history has evolved over the years, including the scope of topics covered as well as the profile of the speakers themselves. I suspect that some of you will spend hours listening to these talks.