Institute for Precambrian Geology and Geochronology - Russian institute for the study of the Precambrian, with English sections.Geological Time - Lecture notes on different methods of measuring geologic time.
Geologic Time - USGS on-line publication about the relative and radiometric geologic time scales, age of the earth, index fossils, and related topics.
Berkeley Geochronology Center - Non-profit scientific research institution dedicated to establishing the history of the Earth, its various inhabitants, and its interactions with the rest of our Solar System, throughout the 4.6 billion years of our Planet's existence.
Earth History - a synoptic time table.
Web Time Machine - Geologic time scale with links for each time interval.
