What's your favorite Google earth app?

What's the coolest, strangest, most interesting, most innovative or most useful thing that you like to do with Google Earth? Many of us regularly use G. Earth to track hurricanes, sightsee, check out National Geographic magazine, shop for real estate, or ??? I'm interested in hearing about what you'd must have Google Earth utility or tool is. Please share a small description and a website and/or KML link... I'll be summarizing some of the findings and sharing with readers. Respond with a comment or simply blast your submission to googlefun@gisuser.com - what's one of my favorite things to do in Google Earth? Well, I like to check out the recent earthquakes recorded by the USGS (http://earthquake.usgs.gov/eqcenter/catalogs/eqs7day-age.kmz) its also cool to explore the Arctic. On a related note, I also am a fan of shopping on craigslist so the allurstuff app is way cool for an interesting gmaps mashup! Once again, send your submission to googlefun@gisuser.com