Farecompare.com sends e-mail alerts a few hours before price reductions are loaded onto the airlines' reservations systems. Choose when you want to be notified -- for example, if a fare goes below a certain amount. The site also has pop-up charts showing you when travel is cheapest on a specific route. Travelocity.com keeps tabs on airfares with FareWatcher Plus: Select up to 10 destinations and get an e-mail when prices drop. And Yapta.com (Your Amazing Personal Travel Assistant) tracks prices -- and notifies you if the ticket you've already purchased falls in price. The site explains how to contact the airline for a refund -- and may make the request for you. Even if you have to pay a penalty, it could save you money.