What will a post apocalyptic economy look like? Nobody can really know. It will depend to a great extent on what the precipitating event is. If it is an economic meltdown we will be left with one type of situation, a pandemic, or a nuclear war would both leave very different situations. No matter what the event, the first few months will be chaos. Think hurricane Katrina. I think that if a powerful government response is not forthcoming, we will probably see the development, over time, of a kind of decentralized group of independent communities based on an agricultural economy, something akin to the many small feudal kingdoms of medieval Europe. I think that without the ability to provide power, water, and sanitation; the large cities will be doomed. I believe that most human effort will be directed toward producing food and the other very basic necessities of life. There will be little call for occupations that do not produce tangible goods or necessary services. At first, independent communities will have to be highly self-sufficient, producing all necessary the goods and services within the community; but, over time, trade in goods and services will develop between communities. Banditry and inter-community conflicts may be a problem, calling for the establishment of community protection organizations.
I feel that once some sort of trade develops it will probably be based on a barter system. Without a strong central authority, currency and coin will have no value. Some say that gold and silver will be used, but I don't agree. The only way that gold and silver have value is if we agree that it has value. There are so many people today, and so little gold and silver, that most Americans have probably never even owned a gold coin and only a few more have probably had silver coins. Gold and silver have been out of common usage in this country for so long that I don't think most Americans have the proper mind-set to see it as having any intrinsic value. There is a long list of things that most people would probably rather have than a silver coin.
So what kinds of things would make good barter items in a post apocalyptic society? To answer this question let's look at some trading systems from the past.
The Salt Trade
Salt is a mineral that we basically take for granted today. Most of us get too much salt in our diets. Salt is in all of our foods, it sits in shakers on our tables, and every time we get take-out food they hand us packets of it; but it hasn't always been this way. You see, a certain amount of salt is necessary for human health, and in the past salt has sometimes been a hard commodity to come by. Roman soldiers received part of their pay in salt. This is where the saying that a "man is worth his salt" comes from. It is also the Latin root for our word "salary." Salt caravans still make their way into equatorial Africa where natural sources of salt are scarce. There are places in Africa where if you give a man a handful of sugar and a handful of salt, he will throw the sugar on the ground and eat the salt. When it was discovered that salt could be used to preserve meats and vegetables, this only increased salt's value. Many early American settlements developed because of their proximity to salt licks of salt springs. Boiling down water from salt springs to obtain the salt was a common colonial industry. So I would put salt high on my list of valuable barter items, and at about $10 for 50 pounds it is far more affordable than gold.
The European Trade with the Far East
In the Middle Ages when Europe began to develop trade with the Far East, many of the items imported were luxuries. Today many of those luxuries have become virtual necessities to us. Many of the spices that we use in cooking today were rare and valuable in the Middle Ages. Pepper, for example, was valued at its own weight in gold. Most of these spices are relatively inexpensive today, but that is only because of global trade and cheap transportation costs. If trade and transportation were interrupted you would once again see the price of spices soar. Who can imagine cooking any kind of meat, these days, without pepper to put on it. Other spices that can only be obtained by import include cinnamon, cloves, nutmeg, and turmeric. Try to make a decent jar of pickles without these. You will want to lay in a good supply of spices for your own use, but some extra for trade items would not be a waste of your money.
The Western Fur Trade
Before the white men came in search of furs, the Native Americans of the far west had a perfectly functional society. Nature provided them everything that they needed and had been doing so for thousands of years. This makes the Western Fur Trade a perfect laboratory to answer the question of what items an already self-sufficient society would like to add to its economy, if they could get them; and it is an interesting list. Some of the items are to make their daily lives easier, some items are luxury foods, some items are for self adornment, and some items are purely recreational.
In the make life easier category we have things like guns and ammunition, metal traps, metal cookware, blankets, cloth, thread, needles, fish hooks, knives, and axes. Luxury foods would include coffee, sugar, flour, dried fruit, and spices. Beads, ribbons, and jewelry were for self adornment; and recreational items included liquor and tobacco. Quiet an interesting list. Most of these same items will probably still be in demand, although standards for self adornment have changed somewhat over the years.
Two other important trade items will probably be food and medicine. I believe that food will probably be the first important export item of communities that can produce a surplus. Heirloom seeds, bedding plants, herb plants, and breeding animals will also be in demand. Medicines will be hard to come by since most of our modern medications depend heavily on manufacturing and transportation. Medicines would be a very good item to stockpile, especially if they have long expiration dates. Medicines for pain, diarrhea, and infections will always be in demand. Many medicines are viable for much longer than the listed expiration date. In general, dry powder or tablet medicines will store longer than liquids. Check with your physician to see how long you can safely store medicines.
One final word. Skills will be a valuable trade item. Learn how to do something that people will need. It may be making pottery, carpentry, blacksmithing, sewing, wine making, or any number of similar skills. It could be a fun hobby now and a valuable skill in the future.