Geophysics
The Earthquake Resource Guide from Online PhD Programs - a good collection of earthquake information.
Up to date GPS measurements of plate movement from around the world. Displayed on a world map or as graphs for individual stations
The centre is the country’s focus for oceanography and represents an unparalleled investment in marine and earth sciences and technology in the UK. There are detials on the research done at the centre, including the recent "missing crust" story: http://www.noc.soton.ac.uk/nocs/news.php?action=display_news&idx=349
If there's place to get palaeogeographical maps then this is it! There are separate maps for each time period in geologic history, plus some data on past climate. Well worth a visit.
A brilliant strategy game based on finding oil using money left by a deceased Aunt. Uses a Java applet and comes linked with pages to do some reading before you start. From the American Geological Institute.
Some excellent Java applets that let you locate an earthquake using seismograph readings. The site may take some time to load but it is worth it.
All about impact craters on Earth.