Visualising numbers

It is only distantly related to OR/MS, but I have touched on the problem of guesstimates before, as it is a sign of numeracy (an essential OR skill) to know when numbers "feel" right. So I was pleased to see the megapenny site which has pictures of what large numbers of one cent pieces will look like and weigh. In these days of governments bailing out banks and othe financial concerns, it is instuctive to note that $18 billion is just enough to fill the Empire State Building with one cent coins.