Top 10 Airfare Alert and Listing Sites

We all know that there are airfare search sites such as Expedia, Priceline, and Cheapair.com. But then there's a whole different animal: the airfare listing and alert site. Sites in this latter category, which is growing at a rapid clip, may include a search component, but they also provide a list of low fares and/or alerts about such fares, either delivered by email or posted online. In alphabetical order, here are ten of the best. By George Hobica, Airfarewatchdog.com