Some swap with neighbors for necessities, some use computerized trade credit for a trip to Vegas: among both back-to-basics types and live-it-uppers, barter, it appears, is booming, with an estimated eight million people putting their goods and services into the pot. This survey of the scene explains the operation of big-volume barter clubs (""I only use cash,"" says one booster, ""for tips and taxes""); touts the social benefits (equality, reciprocity, trust) of voluntary, nonprofit networks and exchanges; lists the cardinal rules of one-to-one horsetrading (#4: ""Make the deal complex, so only you can follow it""); and advises on the gentler art of negotiating a friendly exchange. Also on the docket: how to avoid paying taxes--a big attraction--without risking fraud. And, to clinch the argument, you'll spend a week with the Taylors of Tucson, a family of five living well on a cash income of $4,500 a year--and the equivalent of $9,000 in barter: she's a weaver with other artistic talents, he's a garage mechanic, their offspring have a precocious eye for relative values. A directory of barter organizations is appended for those tempted to try.