Cambrian
Links
The Dawn of Animal Life
http://geol.queensu.ca/museum/exhibits/dawnex.html
Exhibit about the first animals. Mostly Cambrian, some PreCambrian.
The Cambrian Period
http://www.ucmp.berkeley.edu/cambrian/camb.html
University of California Museum of Paleontology introduction to the Cambrian.
Cambrian Geography
http://vishnu.glg.nau.edu/rcb/Cambrian.html
Description and maps of the continents as they existed at the time.