NASA
Nasa: Earth: Overview: Our Home Planet
Provides a comprehensive look at the planet Earth including photos, how Earth got its name, and facts and figures about its size, seasons, moon, atmosphere, rotation, and lithosphere.
Other
University of Texas Arlington: Isostasy, Gravity, Magnetism, and Internal Heat
An in-depth look at how isostasy works and the processes taking place during glaciation and the melting of glaciers. Looks at gravity and the effects of density differences within the crust and mantle, and at Earth's magnetic field and...
Other
Nevada Seismological Laboratory: Plate Tectonics, the Cause of Earthquakes
This site contains an in-depth explanation of the causes of earthquakes as they relate to plate tectonics, and also has many nice and easy to read pictures, maps, and diagrams of plate tectonics and earthquakes.
Other
Interactions Between the Atmosphere & Hydrosphere [Pdf]
A discussion of the interactions between the four spheres of Earth and how they affect weather and climate. The slideshow is divided into two parts. The first deals with interactions between the atmosphere and the hydrosphere and the...
Other
Jules Verne Voyager: Gem Global Strain Rate Map
GEM GSRM uses a texture underlay grid showing the 2nd invariant of lithospheric strain rate, with an image overlay of coastal outlines in white - which forces the texture underlay to have a black background in regions of zero strain...
Other
Plate Tectonic Theory [Pdf]
Check out this slideshow on Plate Tectonics-The unifying theory for all other theories in the Earth sciences-Has resulted in a more detailed understanding of Earth history-Has enabled geologists to more precisely(and cheaply) discover...