You've shopped around and bought your flight at the lowest fare you can find. But could you have gotten a better deal by waiting? Open a free account with Yapta.com and enter your coming flights. If any fares drop, Yapta will send you an e-mail with instructions on how to get a refund for the price difference or a credit for a future flight. (Note that this works only if you bought your ticket directly from the airline and that some airlines charge a fee to give a refund or credit.) Yapta made its debut in May 2007 as a tool you had to download, but a recent upgrade made all its features available on its Web site.