Big Feet . . . Big Footprint

Lately I've been interested in the idea of sustainable living, and in particular the (counter-intuitive) idea that living in a large metropolis like New York City is much more sustainable than living in a suburb. (There's a great New Yorker article about this from 2004 which unfotunately I can't link to, but if you have the complete New Yorker DVD set I recommend "Green Manhattan".) The reasons are varied but include more efficient heating, cooling, food distribution, and of course widely-used public transportation.
Anyway, I found this fantastic little site that allows you to figure out your ecological "footprint" based on how many acres of land it takes to sustain your food needs, to absorb your carbon emissions, etc. Check it out -- despite the annoying universal front page that makes you choose a country/language.