Booking Flights (Overall)
Comparing top aggregators (for a definition, see page 108) Sidestep and Kayak, we found that eight-year-old Sidestep's flight tool has a slight edge: A handy matrix at the top of the results page gives an overview of the lowest prices pulled from 600 airlines across 200 sites. And refining the search by departure time or airport is a breeze.
Researching Low-Fare Carriers in Europe
Don't get stuck on the name. This is a great resource for learning about 45 low-fare carriers in Europe. Select your two endpoints (say Rome and Oslo) and learn who can get you from one to the other on a direct flight (Denmark's Sterling Air). Caveat: FlyCheapo only shows you who flies where; for prices and schedules, you'll have to visit the airlines' own sites.
Locating the Best International Airfares
Decide how much you want to spend and when you want to travel, and Getaway Maps will overlay the lowest fares pulled from more than 500 airlines (most of the major U.S. carriers, as well as many international ones) for a select range of cities.
Knowing When to Book a Flight
Buy now or wait for a better price?Farecast uses historic pricing data to help you make an educated decision about whether or not a fare is likely to fluctuate in the coming week. A supplementary service called FareGuard ($10) covers the difference if they tell you to wait for a price to go down and it rises instead. Caveat: Farecast covers only 78 cities, all of them in the United States.
Booking Hotels (Overall)
This two-year-old aggregator scours 159,000 hotels worldwide, and about 10 percent of the places that it turns up have been suggested by real people, so the picks are well-rounded. (Hotels.com only lists 70,000 properties.) New features allow you to sort the listings by location (using Google maps) and view photographs.
Finding Late-Breaking deals on Luxury Hotels
Search hotels by ratings in your city of choice, and the site turns up an impressive mix of reduced rates on rooms at luxury properties. Our recent results: 23 percent off a room at the Biltmore, in Coral Gables, and 15 percent off at the Goring, in London. Caveat: The best deals take digging.