For almost a year now, I have been hoarding all pre-1982 (copper) Lincoln cents. As you may have heard, the reason why the U.S. government changed the metal composition of the Lincoln cent in 1982 is that the cost in copper was higher than the face value of the coin. Before 1982, and even through part of 1982, all Lincoln cents contained 90% copper. All Lincoln cents made after 1982 to today, are mostly made of zinc clad on a thin layer of copper.
I have about 30 pounds of pre-1982 Lincoln cents. I weighed a pound worth of copper cents and the face value of that pound was $1.40 U.S. So I can surmise that if cashed in my copper cents, I would get approximately $42 U.S. dollars. However, were the government allow me to melt the cents and sell the copper, I would get about $93 U.S dollars (based on the price of copper as of today, November 21, 2012).
Of course, this is all academic at this point. It is illegal to melt U.S. Lincoln cents; period. I am hoping that by the time this changes, I will have a lot more copper cents and the price of copper will be higher still.
Unfortunately, the only source of copper cents for me is the ground. I have to find them with my XP Deus metal detector and I have to dig them out of the ground.
Fortunately, I love metal detecting and the profit to be made is entirely coincidental.
Happy Hunting and thank you for looking!
The Dirt Is Good To Me 
Funny you say this. I always finger through the penny trays at gas stations looking for wheat cents that have survived. Tonight the attendant told me an old guy goes in and pulls all cents older than 82. Do you really think the government will ever allow melting? Why not melt them yourself and then take it to the recycler..
There was a time when it was illegal to melt silver coins but now it is allowed. I think the copper pennies will follow the same path. As for me melting them, well, no need to risk getting in trouble. I will patiently wait for higher copper prices and for the sure-to-come permission to melt.