The Zoombinis games are _excellent_ math software, appropriate for children ages 8-12. Help from a parent or older sibling may be needed. These aren't your traditional arithmetic drill games, though. They expose kids to logic puzzles with lots of problem solving--critical mathematics skills.
In fact, if you don't tell your children these are math games, they'll likely have no idea. Google "Zoombinis". Available for both Macs and Windows machines. Looks like there are at least three games. I've played and used the first one, "Logical Journey of the Zoombinis."
Very highly recommended. I'm an elementary school teacher, and I use Zoombinis with my fourth graders.
Doug