Someone posted this site on another forum... and frankly, I think it's awesome .

http://www.newgrounds.com/portal/view/525347 

just hit play, then you can scroll through all the different sizes, all the way from the Plank length to the estimated size of the universe!  What I found coolest was actually the fact that the area around human-size was by far the most densely populated order of magnitude.  Since there's really no reason to expect that's due to anything other than "we see things which are approximately our size," it's awesome to me to wonder what must also be filling the very big and the very small, that we haven't even discovered yet.