Other
Moorland School: Earth Science Zone: The Structure of the Earth
Take a look at the Earth from the inside out. This site shows the different layers of the earth with an explanation of the rocks and materials in each layer. Includes a quiz on the structure of Earth.
Nine Planets
The Eight Planets: Earth
Excellent Eight Planets site that provides a vast amount of information about planet Earth. Very comprehensive and complete site.
National Geographic
National Geographic: Encyclopedia: Mantle
An in-depth look at the structure and composition of Earth's mantle, with lots of visuals. Covers lithosphere, Mohorovicic discontinuity, asthenosphere, transition zone, lower mantle, the d double-prime region, mantle convection, mantle...