When I saw copyrighted AP wire service shots of this, I realized that somebody in flickr probably had a few shots as well, marked as public. What a way to get around copyright problems!
This set of photos from flickr user mgc1005 show the Common Cents 17th annual Penny Harvest, "a national educational program designed to teach children about their value as contributors to society." Apparently the kids collect them for charity, and they've collected 600,000 pounds of them.
They take up 30 feet by 165 feet of space.
But some coin people say the word "penny" is not appropriate for the US Cent, and that the only true "penny" is the British penny. One piece of evidence: the plural of these things is "cents", not "pence" as the Brits say.