The math isn't easy, I suppose that's why it's call Math Challenge. Great graphics that will hold a child's interest. Here's a wonderful site tied to the NCTM standards for all grade levels and part of Marco Polo. A computer simulation to teach about the stock market. Young and old can learn what it is and how it can work for them.
Tutorials are available on how to use the stock market and how to pick good stocks.
Learn more about how scale, coordinate systems, and projection figure into cartography. A collection of word problems and interactive exercises will put your mapmaking skills to the ultimate test.