This is a much better visualization of the earthquake data than the static image on the USGS website. Really cool usage of google maps. I wonder if it could do a worldwide map, there probably are a lot more earthquakes in the rest of the world!
USGS GeoRSS feed: http://earthquake.usgs.gov/earthquakes/catalogs/7day-M5.xml
http://thumbtack.github.com/rotarymaps/ (mouse wheel zoom)