Updated post: It's rare that we get to cover math here. So here it goes: Adrian Banner, a lecturer at Princeton, has put together a lecture series (in video) that will help students master calculus, a subject that has traditionally frustrated many students. The 24 lectures (get them on iTunes) were originally presented as review sessions for Princeton introductory calculus courses offered in 2006, and each runs about two hours. It's worth noting that Banner has used the lectures to develop a handy book, The Calculus Lifesaver: All the Tools You Need to Excel at Calculus. To find this course (and many others like it), look in our collection of Free Online Courses from Great Universities. Here you will also find MIT's course, Single Variable Calculus, which now appears on YouTube and iTunesU.