For those following for math in general, I will add:

BrainPop Jr

BrainPop

Mathletics

Like Tonysemail, we also enjoyed IXL, and, as mozar noted, khan academy is great. (I haven't tried coursera for a kid yet.) These sites were all awesome during our homeschooling stretch. Conventional school methods have been poor for him. I'm setting him up for online math over the summer, but am really excited about the link posted by Lis (thank you!!) re: woodworker math, just because he will be super motivated and excited to do math that makes sense in the context of his current hobby. My dad had only elementary school, but was an absolute whiz with "woodworking maths", learning applications as he went within that context.

Lis, in three days of woodworking, this has what has come up: angles/degrees, adding fractions, dividing fractions (even just in half), measurements of 8ths and 16ths, understanding that 1/4 is the same as .25 which is the same as a section of pie (i.e., relating the concepts).