The other day I was talking about how people in Greece were preparing for the crash by buying appliances and I suggested they would be better off buying a water filter for their home as FerFal pointed out during Argentinian crash the government didn't have the money to buy water treatment supplies and chemicals making even the municipal water dangerous to drink the guy just could get, but was proud of the fact that he had prepared for a crash here by buy good sturdy kitchen appliances himself.
Check out the LifeStraw line of products.
Individual carry around, PLUS the ‘family size’ with a funnel.
Water and waste are the biggies. Food for anything up to a few years is pretty achievable; in the absence of water and sewer, those of us in cities are hosed without an alternative. No problem to have a year or two of canned and freeze dried goods, but storing or purifying water and disposing of waste are more difficult and more critical to sustaining life and health.