Sacagawea Dollar Obverse

Chris Guillebeau, author of the $100 Startup knows a thing or two about traveling the world. His secret: free mile bonuses from various credit cards.

Once, he rented a shopping cart from a homeless man to help push $2,000 worth of Sacagewea dollar coins to the bank. The US Mint sold the coins at face value, with free shipping. If you bought the coins with a frequent flier mile credit card, you could deposit the coins and keep the miles for free. Total, Chris bought $30,000, netting himself 30,000 frequent flier miles. (The Mint has since set purchase restrictions.)