This article from Rueters details a whuffie system that co-habitates with US currency. The BerkShare is valued at .90 on the US dollar, and is mostly used by locals of Great Barrington, Massachusettsas a way to give a 10% discount. The Berkshare comes in denominations of 1, 5, 10, 20, and 50. It is illegal for a state to issue it's own currency, however coupons are permitted as long as they do not resemble US currency. A local bank is hoping to convert Berkshares to a debit card.