Earthquake Mapping: I'm working through the app dev book I mentioned a week or two ago. One of the examples I'm coding up grabs real-time earthquake data from the USGS and plots it on Google maps. I tweaked the overlay code to show the quakes with disks proportional in area to the magnitude of the quake (r=sqrt(10^mag/pi)). Well, I think it's pretty cool.
That is pretty cool.