If any, what are some SAT or ACT Prep courses or programs that you've taken during high school? How much did it cost? And was it helpful in anyway?

This summer I enrolled in the Revolution Prep course to study for the SAT. It was only $400 for five weeks, but I was able to raise my score nearly 400 points! My essays are now killer.

I never took any SAT or ACT prep courses. I did, however, purchase a bunch of books published by both Kaplan and Princeton. That was helpful in getting me into the test mentality.