When the national government and central banks that don't manage that well, you get local banks vacuuming out people's deposits. The local communities end up with a currency deficit when their local return on investment can't compete with the return elsewhere in the world. Some places keep track of exchange credits on local computer bulletin boards. The dentist does trades with the accountant, and so on. This enables a community to have an alternative, complimentary economy.
People have their community accounts in one pocket, pounds or dollars or francs in the other.
Ithica, New York has good working model of this going. Joe's Restaurant says it will accept 30 percent of the tab in Ithica money and 70 percent in U.S. dollars. The guy down the street wants to compete, so he says he'll take 50 percent in Ithaca credits, and so forth. Som municipalities use volunteer credits to give people free seats on the buses, for instance. The purpose of this measure was to maximize war production.