It's already happened to me twice this year: I bought airplane tickets only to have them go on sale a week later. So much for planning ahead! While I've had good luck with Orbitz's price assurance, their prices for tickets can be a bit higher than if you purchase directly from the airline.

If you've ever had a similar experience, you'll be happy to hear about the new MasterCard Price Assurance program that's free to MasterCard customers. You simply register for the program at priceassure.mastercard.com and use your MasterCard to purchase plane tickets. MasterCard alerts you if your fare dropped and you're then able to pursue getting a credit from the airline on future tickets. Sweet deal!