Enrico Bertini, who has taught information visualization at New York University for the past few years, put up his class materials for open use. There are lecture slides, exercises, and a course diary of his own teaching experiences. Should be useful if you want to teach or learn on your own.
Back in my day, I didn’t have formal visualization courses. I checked out paper books from the library, pieced together tidbits of Flash tutorials meant for games, and walked in the snow for five miles to and from school. Consider yourself lucky.
