University of California
Ucmp: Divisions of Precambrian Time
This site provides a brief overview of the Precambrian Era and provides a clickable chart that breaks down this era into five different time frames. A lot of info is provided on each of the five.
University of California
Ucmp: Web Geological Time Machine
The Museum of Paleontology at Berkeley offers an online geological time machine which allows you to catch a glimpse of ancient eras in earth's history. Click into an "Era" to learn about its stratigraphy, life forms, localities, and...
University of California
University of California Museum of Paleontology: Geology and Geologic Time
This site provides information about the geologic relationships of rock layers, as well as much about geologic time and the history of Earth.
Center for Educational Technologies
Earth Floor: Geologic Time
This is a nice explanation of geologic time and Earth's major eras. Although this site is designed for younger students, it is mostly text with few images.