Open Questions: Geologic History of the Earth

PhysicalGeography.net: "An educational web portal that focuses on" physical geography. The site includes an online textbook, glossary, and external links.
The Physical Environment: An Introduction to Physical Geography: Online textbook of physical geography, by Michael Ritter. There is also a blog maintained by the author.
West Australian find sets back Earth clock: January 2001 news article about discovery of 4.4 billion year-old minerals that indicate Earth may have cool enough to allow life to develop earlier than previously supposed.
Record of Earth's history found in ancient rocks: August 2000 news article about evidence from sulphur isotopes that atmospheric oxygen levels rose significantly between 2.5 and 2.1 billion years ago.

The iron record of Earth's oxygen
Sid Perkins
Science News, June 20, 2009: Scientists are decoding the geological secrets of banded iron formations.