Is anybody familiar w/ or use Whyville? Here is a little blurb about it. Since its inception in 1999, Whyville has grown to a population of almost 3 million registrants and a run rate of 35 million page views per month. Every day, tens of thousands of children from around the world visit to interact, have, and explore topics in science, economics, citizenship, and more.
Click here for more info (the Whybrary sounds really intriguing)