One of the true marvels of the internet-age, MIT’s OpenCourseWare project makes video lectures, notes, problem sets, and exams from over 2,000 MIT courses freely available to anyone with an internet connection.
Naturally, MIT’s OCW project offers courses in technical fields like Mathematics, Engineering, Chemistry, and Computer Science. But many humanities courses, in subjects such as Literature, Foreign Language, and Music, are also available. You can browse all of the courses here: http://ocw.mit.edu/courses/.
The Multivariable Calculus course has been especially helpful for me. Not only can I brush up on techniques in vector calculus, but by watching the lectures I get a different teaching perspective on the material. Browsing the problem sets and tests gives me ideas for my own assignments and assessments. And, naturally, it’s a wonderful resource for the students!
I’ve also enjoyed making my way through some of the advanced statistics and physics courses MIT has to offer. As a teacher, it’s always nice to remind yourself how lost one can be as a student!