A certain Leo Fair pointed out that I had never mentioned Khan Academy here. This must change.
Khan Academy is an educational site with videos designed to help you learn things. A lot of the topics, especially the more fleshed-out ones, focus on math and science, but there are also a lot of videos in economics and even a few in history. The math topics are the most fleshed out of the topics; you could probably start at the most basic math topics and work your way up to differential equations and linear algebra with Khan. Heck, I could probably use some of these topics as a review.
The real question is why I didn’t know about this site when I was taking physics. Maybe I would have done better with these videos than I would have just looking over my notes before the quiz and doing a few problems before the midterm and final. Maybe I can make up for that by using Khan now.