The IRIS Consortium
http://www.iris.edu/

Click on an earthquake location on the Seismic Monitor, an interactive map of world seismicity, to monitor earthquakes in near real-time, view records of ground motion, and visit seismic stations around the world. The display is updated every 30 minutes, using data from the National Earthquake Information Center. Site maintained by the Iris Consortium, a university research consortium dedicated to exploring the Earth's interior through the collection and distribution of seismographic data.

Earthquake Information from the USGS
http://quake.wr.usgs.gov/

This site, from the Menlo Park, California, field office of the U.S. Geological Survey, is full of useful information: maps and lists of recent earthquakes, an earthquake FAQ, links to related sites, and, for those who aren't convinced of impending danger, a section entitled "Hazards and Preparedness: Why and How to Prepare."

USGS Pasadena Earthquake Information
http://www-socal.wr.usgs.gov/

Repository for California Earthquake Fault Models, so you can see exactly what went down in some major California quakes. Also has earthquake catalogs, source models, current seismicity maps, lists, reports, and probabilities. From the folks at the Pasadena field office of the USGS.

Electronic Desktop Project -- Virtual Earthquake
http://vflylab.calstatela.edu/eec/Earthquake/

An interactive, educational computer program that shows you how to locate an earthquake's epicenter and determine its Richter magnitude. (Upon completion of this activity, should you so desire, you can receive a personalized Certificate as a "Virtual Seismologist" from the site managers.)

University of Nevada at Reno Seismological Laboratory's Helicorder Camera
http://www.seismo.unr.edu/Webcam/webcam.html

There's a live cam on one of the seismometers at the Nevada Seismological Laboratory; or, if that's dull on a non-earthquake day, view a movie showing the device after a quake on Nov. 27, 1996. Or test out the new JavaWorm real-time earthquake monitor for Nevada and eastern California.