Is Junior having trouble mastering the art of multiplying mixed numbers? Think you might have to hire him a tutor? Save some money and visit KhanAcademy.org instead. Former hedge fund analyst Sal Khan (hint: he's pretty good at math) will teach your kid to add, subtract, divide, and multiply -- for free. When you're done, have Khan explain how the U.S. Electoral College works, why the Greek debt crisis is important, and how a black hole works, too -- also all for free.