Finding the cheapest airfare is a game -- and often, a maddening one at that. Flight prices fluctuate all the time, and the only way to monitor all the ups and downs is with frequent searches. This can obviously lead to shopping fatigue: Who has the time to punch in dates and destinations into a handful of booking engines several times a day?

A few websites have begun doing the searching for you. (More on those sites in a moment.) The best option of all may be a new site, Yapta.com. Still in beta-testing stage, the site's entire mission is to handle all the searches for you. Members plug in their dates and routes, as well as a price threshold. The site does several price searches per day, and as soon as the flight drops to that specified price, the member gets an e-mail alert. Members can also download Yapta's software and get messages instantaneously on their desktops, if they prefer. Membership is free, though so far the service isn't available to the general public. Perhaps by this summer it'll be available to everyone, the company says, but nothing's been decided for certain.

As a member of the media I've been given a sneak preview of the site and have been testing it out. A couple things to note:

For Yapta to start working for you, you've got to plug in exact flight numbers and times. The service searches for fares on that specific trip only; it doesn't search fares for an entire date. That may be good (if you're only be happy with that specific flight) or not so good (if you're flexible with times and are only looking for a cheap fare).

If you download Yapta, there's a "trip tagging" service, in which with a couple quick clicks you can automatically begin tracking prices for specific flights you see at any airline site or major booking engines like Expedia. It's easier than doing searches at various sites, jotting down flight numbers, and then entering them at Yapta.

Yapta not only tracks flights you might want to buy, it tracks flights you've already bought. Why? Because occasionally fares drop so low that airline ticket holders are entitled to a cash refund (minus a change fee of $100 or so). It's rare but does happen. Yapta also tells members when they're entitled to a flight voucher from an airline; it's a little-known rule with some airlines that a ticket-holding passenger can get a flight voucher if a sale is announced and prices drop below the fare the passenger paid. Getting the airline to cough up cash or a voucher involves some red tape, as you'd expect. But the only chance of getting anything back from the airline is by tracking fares after you've already paid for your flight -- and nobody wants to do that. So Yapta, it seems, will certainly come in handy. We'll let you know when it's open for business.

In the meantime, there are two services that are already available, though they are far from perfect as of yet. In early 2005, Southwest Airlines released its Ding! feature, in which you could download software to your desktop and an audible "ding!" sound alerted you of messages from the airline that often involved flight sales. The problem was, many of those messages were useless, the "ding!" quickly becomes annoying, and I prefer to avoid downloading software if it's at all possible. Also, there's the obvious point that all of these messages are only about one airline.

Expedia recently released its Fare Alert feature, which also must be downloaded (another downside: It doesn't work for Macs). You plug in a route and a price threshold and get an alert once Expedia detects that the threshold has been met. The big problem here, beside the fact that Expedia doesn't search some low-fare carriers, is that Expedia doesn't really do price searches for you. Instead, Fare Alert relies on Expedia customers: If one of them books a flight on Expedia that matches your criteria, you'll get a message. But if no one books such a flight, you won't hear a peep, even if there's a fantastic sale.

We'll tell you more about Yapta and other fare alert services as we learn about them and test them out. Until then, we'd love to hear about any of your experiences using fare alerts or tracking prices on your own.--Brad Tuttle, senior editor of Budget Travel.