If you're a student, or teacher, or homeschooling parent and you've not heard about the Khan Academy you owe it to yourself to check it out. Salman Khan quit his career in the financial world to teach the world via videos. If you look on Khan's Youtube Channel you'll see videos on biology, linear algebra, chemistry, calculus, statistics, physics, differential equations, algebra, arithmetic, GMAT problem solving, pre-algebra, trigonometry, probability, geometry, precalculus, Singapore Math, and more.
Khan has also made videos of all eight Math SAT practice tests in the College Board's Official SAT Study Guide. Wow!
Here's a great promotional video of Khan's work:
Hat tip to Murray at squareCircleZ.