BethG -- my ds7 is the same way. He likes doing math, and he's good at it. I highly recommend the Fred books for a quick learner -- we have the Fractions and Beginning Algebra, but I think we need to get Decimals ...
A few weeks ago, my ds7 actually asked if he could start "Life of Fred: Beginning Algebra" after glancing through it (we actually bought it for dh, long story). I told him he had to finish the two prereq Fred books before starting the Algebra one -- and now he's 12 chapters through "Fractions." And doing well.
We've always, *always* have a bedtime story -- either two picture books or two chapters (or a bunch of Calvin and Hobbes!). Since he wants to do Fred but doesn't have a lot of free time with full-day summer camp, I've just starting giving him the summer option of having a "Fred-time story" together instead. We'll work one or two chapters together, and then he'll continue on, or switch to reading a book. It's actually relaxing for him and he likes it.
However ... I'm kind of alarmed at how quickly he is progressing, with relatively little effort. His MAP math score jumped more than 30 points in the past year with no homework or afterschooling to speak of, and is now a bit high for my comfort zone! I really, honestly did not think he could progress this quickly -- and I don't know that I should be assisting him to get further ahead, even if he's asking for it!
I'm getting antsy about what we'll do in middle school and high school ...