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By now, you know that no single travel Web site always offersthe lowest prices. So each time you book a trip online, you feelyou have to check several sites to assure yourself you’re notoverpaying.

Save time by using sites or software that employ”Web-scraping” technology to simultaneously searchmultiple sites and then present prices in easy-to-read charts,making comparison shopping a snap.

SideStep is a free program that you download. Its search engineautomatically launches when you shop for air, hotel or car rentalfares, scouring multiple travel booking sites (including low-farecarriers that don’t always appear on sites, like Expedia orOrbitz) for the lowest prices. While you can’t book your tripdirectly with SideStep, it will provide a link to the page whereyour deal of choice is located.

Cambridge, Massachusetts-basedITA Software helps travel suppliers develop online booking sites,but it also offers consumers a broad and flexible airfare searchengine on its home page (see the “Looking for Airfares”box.) You can check one-way, multisegment, or even internationalfares for flights originating overseas. It also searches fares forairports within a 300-mile radius of your origin or destination, orflights within 24 hours of the flight times you specify.

Like SideStep, this isn’t an actual booking site, but a smallprogram you download that searches multiple hotel-booking sites forthe best rates in more than 58 countries. The end result is anexhaustive array of rates with the lowest ones highlighted. Tolimit the search results in a huge hotel market like New York City,you can enable filters that specify the distance from the citycenter, price or star rating. Once you’ve found the best rate,TravelAxe provides a link to the site, where you can make areservation.

Chris McGinnis, travel correspondent for CNN Headline News,is author of .