American Museum of Natural History
American Museum of Natural History: O Logy: Stuff to Do: Edible Earth
Take a look at the layers that make up our Earth: inner core, outer core, mantle, and crust. Then have fun making a model of the Earth's interior that you can eat up.
Purdue University
Purdue University: Earth's Interior Structure
Purdue University provides a great lesson plan for learning about the Earth's interior structure. Focuses on the crust, mantle and core. Also includes examples and great charts that students will enjoy looking at.