http://www.lewrockwell.com/orig/brimelow3.html
Mises.com interesting stuff.
Basicly as long as government doesn't influance the markets with promises and over regulation. Just let banks issue their own money. These currencies would compete in the market much like international currency exchange works.
Government loves to monopolize money creation. It gives them and their "closest friends" the advantage of inflating the money and saddles the people with all the bad bits.
This has worked in the past but would be kick ass today. Because of instant communications and bank transfers. So long as true free markets are used it will regulate itself. The government need only worry about instances of fraud.
If Citi-Bucks began lossing value you could switch to BofA-Bucks. They would all compete to be the best money. That can only be a good thing for the people. As we might start seeing a steady decline in prices and increase in the value of our pay-checks.