http://finance.yahoo.com/banking-bu.../fly-for-free-us-mint-forbes?mod=bb-budgeting All legal. Basically order specific coins from the US Mint. Use your frequently flier credit card to buy. When they arrive deposit them to pay of the balance before it is due. I guess you could use other cards like cash back but it wouldn't be worth it for the value you'd get. Limit is now $1000 per month. But 36,000 FF miles for free is decent.