Last Updated Mar 22, 2011 11:12 AM EDT
When Gates wants to brush up on a subject he turns to the Khan Academy, which provides free online tutorials to students of all ages around the globe. Khan Academy is the brain child of Salman Khan, a former hedge fund analyst and Harvard MBA, who has undoubtedly become the Internet's most popular educator.
Kahn started creating online tutorials for his cousins in New Orleans five years ago and his lessons, which he posts on YouTube, became so popular that he ended up creating a steady stream of them. Today, the Khan Academy offers 2,200 free videos on such topics as basic math, geometry, calculus, chemistry, economics, biology, physics and even the French Revolution. You can also find free SAT prep tutorials on the site.
For students needing a math tutor, there is a lesson that starts with 1 + 1 = 2. On the other extreme, colleges students can find advanced tutorials for differential equations and other scary hard courses math and science courses.
I decided to check out the Khan Academy after talking to my son Ben, a college freshman, who has decided he needs a tutor in linear algebra. This is the brutal course that science, engineering and math majors take after completing two semesters of calculus. I sent him the KhanAcademy link to nearly 150 linear algebra tutorial lessons.