Once the capitalist system (hypothetically) falls, I feel certain that there would be period of chaos, and certain concepts that have evolved over the centuries of capitalism would have to be relearned and realigned.
1. Property. The concept of property would, I think, evolve toward the Proudhon concept, as referred to by @Kropotkin above, namely, de facto ownership (physical possession) of property will be more legitimate than de jure (legal title).
2. Labor. To quote Abraham Lincoln: “Labor is prior to and independent of, capital. Capital is only the fruit of labor, and could never have existed if labor had not first existed. Labor is the superior of capital, and deserves much the higher consideration.” All things of value would be determined by the amount (and possibly the quality) of labor of production or creation.
3. Commodities: Labor and labor-derived commodities would be the currency. I see a robust barter economy,
4. Technology: given the current state of technology, there is no reason it would all devolve, and that we would be reduced to pre-electrical technologies. The power grid as we know it would deteriorate, and possibly even disappear, as parts are appropriated, but there is a good chance that wind, water, solar and other technologies would develop a local/community structure of generating this technology.