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!
The GeoRSS feed from USGS makes doing simple apps showing recent earthquakes pretty simple. Here's one I did a year or so ago: http://swingley.appspot.com/maps/eq
I've found Polymaps (polymaps.org) to also be great for making realtime geo-dashboards. Combined with CloudMade for map tiles, you can customize the look and feel very easily.