An accurate estimate of the average volume of a human being was a little hard to come by. However, a rough estimate was proposed in a number of sites found in a Google search that hypothesized the following: the human body is approximately the density of water (1.01kg/l [http://en.wikipedia.org/wiki/Orders_of_magnitude_(density)]), the average mass of the human body is around 70kg [http://hypertextbook.com/facts/2003/AlexSchlessingerman.shtml], so the average volume of a human comes in around 70.7 liters.
Next is the simple math of translating a human into a cubic meter:
1hu = 70.7l = 0.0707m^3
1m^3 can hold a little more than 14 people (assuming you hit the puree button on the blender):
1m^3 = 14.1443hu
So how many people are on this planet? That you can find all over the internet:
6.790062216E+9 (July 2009 estimate [https://www.cia.gov/library/publications/the-world-factbook/print/xx.html])
So, again some simple math shows that we human beings, one of the most prolific forms of dry-land life, would take up the massive volume of around:
480E+6m^3 which of course equates to 0.48km^3
That’s right! We add up to less than half a cubic kilometer.
When you read articles that state “The biomass of human bodies now exceeds by a hundred times that of any large animal species that ever existed on land.” [http://www.newstatesman.com/200402230015]
You are left with comparing that to what: how much we use in resources? How about how much biomass was morphed into coal?
Just for some perspective, comparing the human race to the volume of coal mined on a yearly basis [http://www.lewrockwell.com/reisman/reisman15.html], I found this interesting article that noted in 2004 approximately 2.1km^3 were mined. So we could pack the mass of the human race into the hole left over from three months of mining coal.

So it would take just a small portion of the top of Pikes Peak (think about a 1km x 1km x 480m box) to hide the whole of the human race.
If you are a visual person, click on the capture of Google Earth where I mapped a 1km line across the Peak.
We are so small.
And yes, I know I’m weird.
--Marty