Yes! Khan Academy is the go to source! They were very instrumental and supportive in helping in the area of not only for the PMP, but particularly with my struggle with College Algebra. They take a refreshing approach to things and makes things and concepts much easier to understand, I think.

I myself love Khan Academy. It helped me out a whole lot. I will recommend them to anybody.

I have found coursera.org is useful if you want to take project management course. Though you have to pay, but's worth the cost and also it's great to anyone you wants to be in the management position.