The add-ons for Google Maps seem as vast and wide as the places you can click and swoop through there, especially once you go past the First Google Map Thing (finding your own house). A nice example is the Google Areometer, which allows you to click to place points on a map, and once a shape is enclosed, it calculates the area. I cannot help but wonder of the applications for teaching geography, some cool math lessons, generating images for reports, etc. You get the area measured in square meters, hectacres, square kilomoeters, acres, square feet, square miles:
On a very quick and dirty go-around, a clicked a zone around the map area of Grand Canyon National Park:
Obviously, my points area bit off but my mapped area estimates the park size at about 950,000 acres or 380,000 hectacres (what the heck is a hectacre??). How’d I do? Doing a quick Google search, I’m in the ballpark:

So yes, I lost a good chunk on my point placement in the western area of the park. The point is not that its micro-precision, but what can one do in terms of exercises of estimating area, or calculating the amount of land covered by a river system drainage area, or estimating the size of an urban sprawl or which bus route serves the largest area of town…
Go, Google go.
Yet another tip of the blog hat to Tim Lauer for finding something cool!
Hectare (not hectacre). A metric unit of measujrement of area, equivalent to an area 100 meters by 100 meters. Used in nations that use metric measurements.
http://en.wikipedia.org/wiki/Hectare