PaperBack Swap is exactly what it sounds like: a place to swap paperback books. Currently, more than half a billion books are available for trade on the site. Just list the books you don’t want anymore and other members will find them. When someone requests one of your books, you just mail it out and then choose any available book that you want to receive. Swapping is easy, and membership is free.

Trade did occur in non-monetary societies, but not among fellow villagers. Instead, it was used almost exclusively with strangers, or even enemies, where it was often accompanied by complex rituals involving trade, dance, feasting, mock fighting, or sex—and sometimes all of them intertwined. Take the indigenous Gunwinggu people of Australia, as observed by the anthropologist Ronald Berndt in the 1940s:

Corporate barter focuses on larger transactions, which is different from a traditional, retail oriented barter exchange. Corporate barter exchanges typically use media and advertising as leverage for their larger transactions. It entails the use of a currency unit called a "trade-credit". The trade-credit must not only be known and guaranteed, but also be valued in an amount the media and advertising could have been purchased for had the "client" bought it themselves (contract to eliminate ambiguity and risk).[citation needed]
Adam Smith, the father of modern economics, sought to demonstrate that markets (and economies) pre-existed the state, and hence should be free of government regulation[citation needed]. He argued (against conventional wisdom) that money was not the creation of governments. Markets emerged, in his view, out of the division of labour, by which individuals began to specialize in specific crafts and hence had to depend on others for subsistence goods. These goods were first exchanged by barter. Specialization depended on trade, but was hindered by the "double coincidence of wants" which barter requires, i.e., for the exchange to occur, each participant must want what the other has. To complete this hypothetical history, craftsmen would stockpile one particular good, be it salt or metal, that they thought no one would refuse. This is the origin of money according to Smith. Money, as a universally desired medium of exchange, allows each half of the transaction to be separated.[3]
If you need more than clothes, like baby bedding, baby furniture, or even sporting goods, you’ll be glad to find Zwaggle. It’s a network of parents who have joined together to share the expense of getting “new to your family” stuff in exchange for used or no-longer-needed items. You receive Zwaggle points for giving away your things, and you can use those points to get the things you want. Membership is free, and the community is powered by a points system rather than cash. The only money you have to spend is on shipping.

So as you consider items to stockpile, you should think about items that are necessary, but might not take up a lot of space.  Referring back to Mark Goodwin’s book mentioned above, one thing the main characters looked for were canning lids and rings.  They don’t take up a lot of space and in a real collapse situation, they will be really worth it!
An alternate currency, denominated in labour time, would prevent profit taking by middlemen; all goods exchanged would be priced only in terms of the amount of labour that went into them as expressed in the maxim 'Cost the limit of price'. It became the basis of exchanges in London, and in America, where the idea was implemented at the New Harmony communal settlement by Josiah Warren in 1826, and in his Cincinnati 'Time store' in 1827. Warren ideas were adopted by other Owenites and currency reformers, even though the labour exchanges were relatively short lived.[20]