Under the BerkShares system, a buyer goes to one of 12 banks and pays $95 for $100 worth of BerkShares, which can be spent in 370 local businesses. Since its start in 2006, the system, the largest of its kind in the country, has circulated $2.3 million worth of BerkShares. In Detroit, three business owners are printing $4,500 worth of Detroit Cheers, which they are handing out to customers to spend in one of 12 shops.

By law, local money may not resemble federal bills or be promoted as legal tender of the United States, says Claudia Dickens of the Bureau of Engraving and Printing.

The IRS gets its share. When someone pays for goods or services with local money, the income to the business is taxable, says Tom Ochsenschlager of the American Institute of Certified Public Accountants.

Pittsboro, N.C., is reviving the Plenty, a defunct local currency created in 2002. It is being printed in denominations of $1, $5, $20 and $50. A local bank will exchange $9 for $10 worth of Plenty.

"We're a wiped-out small town in America," says Lyle Estill, president of Piedmont Biofuels, which accepts the Plenty. "This will strengthen the local economy. ... The nice thing about the Plenty is that it can't leave here."