A hack reworking Mike Bostock's US county choropleth map to show response density from the USGS' site from the 2010-11-05 3.2 quake near Piedmont, CA via Yahoo! Pipes.
To view this you'll need to start Chrome with the --disable-web-security command-line switch, or similar for your browser, since gists are rather space constrained and Yahoo! Pipes doesn't seem to let you consume remote content-type: application/octet-stream, or something like that.