Sweet deals abound on packages sold by hotels and airlines. May 1, 2006 New competition is making the hottest product in leisure travel -- custom vacation packages -- sizzle. Although Web travel agencies such as Orbitz, Expedia and Travelocity once dominated this field, many airlines, hotel chains and rental-car companies are getting into the act. And because the top three Web travel agencies lead the market, these newcomers have been offering some attractive custom package deals to grab consumer attention.Custom packages are similar to pre-bundled packages, but they give you options. So instead of having a rigid itinerary and being forced to use certain suppliers, you have options for your airline, flight time, hotel, rental-car company and type of car. RELATED STORIES 25 Best Value Travel Sites Best Cards to Use Abroad When to Insure Your Trip Pursue Your Passion at Adult Camps For example, JetBlue Airways began offering packages on JetBlue.com in November. We recently saw a three-night Memorial Day weekend getaway to the Luxor Hotel and Casino in Las Vegas, including two round-trip tickets from Buffalo, for $1,617 -- $115 less than booking the tickets and room separately. JetBlue flights are sold exclusively through its own site. But don't assume that vacation packages sold directly by hotels, airlines and rental-car companies are always the best deal. On a different search, we changed our hotel and added a three-day, midsize Avis rental car to our package, which whittled our savings down to less than $100 from booking separately. Advertisement Yet in other cases, vacation packages that combine airfare, hotel stays and a rental car can be a good deal. Case in point: United offers package deals via United.com. Recently, a Memorial Day weekend three-night Hawaiian getaway to the Hyatt Regency Waikiki Resort and Spa, including two round-trip tickets from Los Angeles and an Avis economy rental car, cost $1,582 -- 16%, or $312, less than booking the tickets, room and rental car separately through United, Hyatt and Avis. It's to the advantage of airlines, hotel chains and rental-car companies to entice travelers to buy from their branded sites instead of Web travel agencies. For example, Marriott saves when travelers book directly through Marriott.com instead of, say, Expedia -- with which it must split the profit, says Ed Perkins, a writer for online consumer site SmarterTravel.com. Comparison-shopping online for package deals is an inconvenience because you have to enter your itinerary at each site to fetch rates. Search engine Sidestep.com aspires to end this problem by letting you enter your itinerary once to fetch packages from several sources. Sidestep has begun to trawl the package deals offered by Orbitz and a few other travel companies. Rival search engine Kayak.com plans to debut a similar vacation-package service this spring. Both Sidestep and Kayak say they plan to serve up deals from top travel providers and Web agencies soon.