Oregon State University
Osu: Volcano World: Layers of the Earth
This is a website not only on the mantle but also about all the layers of the earth.
The Franklin Institute
The Franklin Institute: Land Mass Formation
The Franklin Institute has provided a demonstration that theorizes how the earth's crust was formed. This is a lesson plan that needs only a few materials.
Treehut
Suzy's World: Earth
At this site from Suzy's World and Suzy Cato, you can find out what the earth is made of and try an experiment.
The Franklin Institute
The Franklin Institute: Earth Bowl
This activity from The Franklin Institute demonstrates the layers of the earth using gelatin, pudding, graham crackers, and a few other items. The young scholars actually construct a representation of the earth that they can eat.