I found that DS6 gets excited about math when he spends time with a mentor who is passionate about math (i.e., not me). For example, my mathy dad got DS excited about learning binary by teaching him about the Nim game. DS wanted to learn the "secret":
http://www.csm.astate.edu/Nim.html.My math/physics brother played the dot/box game (the one where you draw lines between adjacent dots in an array and try to complete more boxes than your opponent) and got DS interested in coming up with a formula for figuring out how many possible boxes you could make with an XxY array of dots (or something like that - I wasn't excited enough to pay too much attention
.
I think there's a real art to teaching math to mathies -- the key is to get them excited enough in a problem so that they *want* to do the grunt work to solve it. I'm sure DS would not be interested in learning binary had it not been for the context of the game. I think the competitive aspect helped too.