Sal Khan is crazy...about explaining things! His "Khan Academy" website has become pretty popular, especially since early 2011 when Bill Gates named Mr. Khan his "favorite teacher". Before that, Mr. Khan enjoyed a bit of fame for his videos back in 2008/09 on just what happened in the credit crunch. If he can make sense of CDOs and credit default swaps, then you can certainly trust him with GMAT math!Mr. Khan's videos are pretty uniform, and his teaching style isn't for everyone (think "electronic whiteboard"). But if you like diagrams and narrated explanations, you can't go wrong here. He has EIGHTY algebra videos (and that's not including his "worked examples"), thirty on geometry, and about a million on pre-algebra and preparatory mathematics, if you're weak on your fundamentals. Oh, and while you're at the site, you can also learn about economics, finance, astronomy, chemistry, history, physics, and biology. Hey, why not? Check it out for yourself:
http://www.khanacademy.org
BONUS! Did I mention that he worked through every math problem in the 11th edition of "The Official Guide for GMAT Review"? If you have it (or the 12th edition; they changed only a small part of the math section), you can "check your work" here, and have the tough problems explained to you. One caveat, however: he doesn't always find the most efficient path to a solution, so sometimes he takes longer than you should on the test. Overall, though, a great resource!
http://www.khanacademy.org/



