You probably know something about what wiped out the dinosaurs, but do you know how scientists figured this out? I just listened to a very interesting lecture on this subject from The Teaching Company. I've bought a few of their DVD and audio courses and I noticed this free lecture listed on my account page. I thought it might be for customers only, but a Google search also found it, so I guess it's available to anyone (at least for now). The lecturer is Professor Peter Ward, a paleontologist at the University of Washington.
P.S. The Teaching Company is having one of their frequent sales and many of their courses are deeply discounted.