Referring to your comment about sorting pennies in your post about nickels : “At present, sorting pennies simply isn’t worth your time. Although I suppose that if someone were to invent an automated density-measuring penny sorting machine, he could make a fortune. As background: The pre-1983 pennies presently have a base metal value of about $0.0226 each.) Starting in 1983, the mint switched to 97.5% zinc pennies that are just flashed with copper. Those presently have a base metal value of about $0.0071 each.”
A penny sorting machine has been developed by a member of the Gold Is Money information community . He goes by the name Ryedale. This machine automatically sorts the pennies into two piles according to composition. [It sorts out the earlier pre-1982 [95%] copper pennies from the newer copper-flashed zinc pennies.] It is exceedingly accurate and the cost isn’t too bad. It can process 3000 pennies in 10 minutes.
There is also another machine out there than can do hundreds of thousands of pennies at a time (from giant hoppers) in a very short span of time, but it is a commercial machine and costs about $10,000 apiece. Contact another member of Gold Is Money  (member name SLV) if interested in learning more. – Ramsey
JWR Replies: Unfortunately, it is presently illegal to melt pennies for scrap. But I suspect that now that it has been more than 25 years since they were last minted, the restriction on melting copper pennies might be lifted.
Even with pre-1982 pennies now worth nearly 2.4 cents , it is still not very economical to launch a business sorting and re-selling pennies. Just to pay for the cost of a coin sorting machine, you would have to sort out and sell more than 1,800 rolls of all copper pennies. Once the value of the dollar drops to the pont that pennies are worth more than four times their face value, then this might become a profitable venture for someone with a good strong back and plenty of secure storage space. Keep in mind that just one $50 bag of copper pennies (5,000 pieces) weighs just a hair over 34 pounds. A $50 bag of the newer debased zinc pennies weighs just over 30 pounds. Ideally, someone could take advantage of the US Mail’s “Flat Rate Box” available for Priority Mail. These have no weight limit! So it is conceivable that someone could use sturdy canvas bags inside these boxes, and some stout tape reinforcement on the outside of the box, and have 34 pounds of pennies mailed anywhere in the US for under $10!
Again, it is not currently very economical to sort copper pennies with the intent to re-sell them. However, if you can acquire some full rolls of copper pennies at or near face value, then it is certainly worthwhile to set them aside.
OBTW, if any readers would care to send their voluntary 10 Cent Challenge  SurvivalBlog subscription payments in the form of either US pre-1982 pennies, or in US nickels (of any mint date), it would be greatly appreciated. Using a Flat Rate Box would be the most economical method. Thanks!