When you make a batch of pickles or jam, you often end up with excess that you'd feel comfortable letting go of for the sake of keeping your pantry interesting. For a few of those excess jars, you end up getting fresh, handcrafted foods for virtually no cost.
Food swapping is nothing new — ancient Babylonian homemakers probably traded olive oil for beans. In modern times, bartering has mostly been associated with poverty; think of the country doctor paid with eggs. But in certain precincts of Brooklyn, where artisanal food buffs have become as ubiquitous as artisanal beards, the lingering recession has combined with a do-it-yourself fervor to fuel any number of edible swaps.