Khan Academy:)
For DS7:
Also, while I found some books on interesting math, our bread and butter is basic numeracy and math facts. I started at the "start." Numeracy (so critical to all elementary level math) and operations: addition, subtraction, multiplication, division. We're finishing up fractions/decimals/percents and will spend some time on geometry concepts, tables, graphs, etc. So, in house, very linear, with some interesting, high level concepts thrown in. I am also a big fan of word problems for applied math.
I do it this way because my DS is a perfectionist and will become extremely frustrated if he lacks foundational skills to solve harder problems (many a meltdown). So you might consider personality differences, when making enrichment choices.
I taught DS7 the way I learned, figuring that when it comes up in school, he will then have a few ways of of arriving at an answer (and he's come up with some interesting methods on his own:)
I literally had to look up how to do things on the internet because I've forgotten and probably wasn't awesome at it to begin with:). I try not to introduce anything that I can't remember how to do-- if I err on a basic problem, my son will tell everyone in sight:)
Here are some things that you can look up and introduce for fun-- perfect numbers (have your sons find the factors of a perfect number). Interesting number sequences, ratios, prime numbers, three dimensional figures, etc.
DS has a goal to reach algebra in the next few years, and his school will accommodate it if he's ready. So, I am making sure that there are few/no knowledge gaps.
