I just got Math Blasters and Zoombinis. He's pretty excited and they look like a good match so far. Thanks for all of the great ideas.
We also have the Number Devil and have read G is for Google. Right now he is reading Sir Cumference and the Dragon of Pi. He giggles every time he tells me about the pie party that lasts for Pi days. He found it at the library last week. The author, Cindy Neuschwander, has written a bunch of "math adventure" books. I suspect we will be looking for more of them soon. Math Curse by Jon Scieszka was also a lot of fun.
Jill
PS I looked at the Larson Math online. That looks pretty good. I think I will sign him up for the trial after school ends next week and see how it works.