With dozens of new travel sites appearing every year, it’s hard to keep track of which ones really deliver. William J. McGee of Condé Nast Traveler has put hundreds of them to the test to reveal the ones that will help you save money, travel smarter and enjoy your journeys more:

Best site for booking airline tickets
Winner: Kayak.com

When to use it: You know where you’d like to fly and want to spend as little as possible to get there.

Why we like it: While it doesn’t allow you to book your ticket, Kayak makes quick work of leading you to the Web sites that offer the lowest prices. It casts a wide net and delivers the best combination of itineraries, prices, and ease of use. It also has terrific tools, including filters that allow you to sort results by airline and airline alliances; takeoff and landing times in both directions; number of stops; flight and layover durations; sites searched; and price. On certain routes, a chart with 90-day historical fare data is provided, as well as the cheapest departure dates.

Caveat: Kayak doesn’t provide all the fare options offered by the airlines, so it always pays to search carriers’ own sites before booking through a third-party site.

Tip: If you’re not sure where you’d like to go, the Buzz feature has trip suggestions based on best fares found in recent searches, sorted by categories as varied as “Top Family Resorts” and “Best Nude Beaches.”

Runner up: In our comparison of ten domestic and international itineraries, we found ITASoftware.com provided the lowest fares for seven out of ten routes, with Kayak ranking second overall. So why not name ITA the winner? Most of ITA’s low fares come from cobbling together itineraries on multiple carriers or with quirky connections that only a travel agent can book.

Knowing when to book
Winner: Farecast.com

When to use it: After you’ve scoured the Web to turn up the absolute rock-bottom fare. Prices change constantly and the cost of that ticket could drop — a lot — tomorrow, or even in an hour. So the key question is when to buy. The Big Three sites (Expedia, Travelocity, and Orbitz) and Kayak all offer features designed to address this issue, but the most innovative responses have come from new entrants, including FareCast.

Why we like it: It uses historical pricing trends to determine whether a fare is likely to drop soon. The site searches 90 days in advance for the lowest fare on a given route, then advises to “wait” or “buy.” How accurate is FareCast? After a three-month audit, Navigant Consulting found the predictions were correct 75 percent of the time, and users saved an average of $55 per pair of tickets.

Caveat: It currently covers only domestic flights to 24 cities.

Tip: Consider purchasing the Fare Guard service for $10 per itinerary. If you delay buying a ticket because FareCast predicts the price will drop within the week, Fare Guard protects you from paying more than the current price—of course you may pay less if the fare drops.

Runner up:  FareCompare.com, which receives fare data from the airlines for flights within, to, and from the United States and Canada, and then posts the prices several hours before they appear on travel agency sites — and sometimes even the airlines’ own sites. Set up a “My Trips” account for alerts on pricing trends and the best dates to book.

Airline reviews
Winner: Skytrax (www.airlinequality.com)

When to use it: Before booking an unfamiliar airline.

Why we like it: A must for aviation geeks and infrequent fliers alike, Skytrax offers user reviews of 560 airports and 545 airlines. The site also evaluates service based on analysis by audit specialists. The seat pitch index alone is worth the visit.

Tip: Read the “Seat Reviews” before choosing your next window or aisle seat.

Runner up: SeatGuru.com. All you need to know about the seat comfort on nearly every major carrier.

Airport and flight information
Winner: Federal Aviation Administration (faa.gov)

When to use it: Before you leave for the airport.

Why we like it: It tells you about delays that the airlines won’t. The FAA’s Air Traffic Control System Command Center (fly.faa.gov) is the definitive source for flight-delay information.

Tip: For further information, use the hot links to the domestic airline sites.

Runner up: Flightstats.com. It allows you to monitor airline punctuality and supplies timely updates.

Security checkpoint wait times: Waittime.tsa.dhs.gov/index.html — the site provides historical records for every screening point at every commercial airport in the United States.

DOT’s Aviation Consumer Protection Division Airconsumer.ost.dot.gov/reports/index.htm— it offers monthly reports on flight delays and cancellations, complaints, mishandled baggage (including pets), and overbooking.

Booking flights in Europe
Winner: Wegolo.com

When to use it: To find great deals on short hops within Europe.

Why we like it: This deep database of low-cost carriers (Ryanair, easyJet, etc.) translates into bargains not always found on other sites. Wegolo searches 75 budget airlines for rock-bottom fares between European cities. Most Americans will feel comfortable on this easy-to-use site: The English-language version features straightforward booking tools and the option of rates in U.S. dollars.

On the heavily trafficked London–Paris route, Wegolo had the lowest fare among seven sites for an itinerary one month in advance. That $160 round-trip fare on easyJet was $17 lower than what Kayak posted (ironically enough, for a rate through Wegolo). For a round-trip booking 90 days in advance between Brussels and Madrid, Wegolo’s fare of $115 was $42 lower than most of its competitors.

Caveat: The European Union recently reported that its consumer rights investigators scrutinized more than 400 European travel sites and found about 50 percent needed improvement in one or more key areas: clear pricing, availability, and fair contract terms. (The names of the flawed sites hadn’t been released at press time; for updates, check europa.eu.)

Tip: The site works best the further in advance you book. It came up empty when we looked for a Rome–Athens flight two weeks before departure.

Runner up:  Opodo.com; Opodo was also competitive, offering a fare of $121 on the Brussels–Madrid route. The site is sometimes called “The Orbitz of Europe,” since it was founded by that continent’s major airlines.

Booking flights in Asia
Winner: Zuji.com

When to use it: To save a bundle on flights throughout Asia.

Why we like it: Zuji, owned by Travelocity, is a pan-Asian portal with links to online agencies based in seven countries; the prices found on those home country sites often yield much bigger savings than you’d find anywhere else. For example, for a 14-day advance booking on a round-trip flight from Sydney to Auckland, Zuji’s Australia-based site offered a nonstop fare on Air New Zealand for $370, which was $284 less than Kayak for the lowest rates on the same carrier.

And Zuji’s Hong Kong–based site posted a $195 round-trip Hong Kong–Tokyo fare on Shanghai Airlines, while the lowest fare on Kayak was $564 on Northwest Airlines. To be fair, the Northwest flight was nonstop, while the Shanghai Airlines itinerary included a connection, but for a savings of more than $300,  we wouldn’t mind a short stop (Kayak didn’t list the Shanghai flight).

Caveat: Fares are offered in local currencies, so you’ll need to convert. Stick to the English-language portals — Australia, Hong Kong, and Singapore (Zuji has sites for several other countries, but they will pose translation problems for anyone who’s not fluent in at least one Asian language).

Tip: The Zuji Travel Secrets page provides user blogs with opinions  on destinations, accommodations, dining, and other areas of interest.

Runner up: Vayama.com performed much better on Asian itineraries than European ones, even edging out Kayak by $28 on the Sydney–Auckland route. The site hosted one million visitors within four months of its launch last June, and promotes itself as being “100 percent focused on international travel,” covering airlines, hotels, and rental car companies in 190 countries. We especially like that it allows access to many foreign low-cost carriers, either through direct links or specialty partner sites.

Last minute travel
Winner: None

There are three well-known players in this arena: LastMinute.com, 11thHour
Vacations.com, and LastMinuteTravel.com. In our tests, none delivered a lower last-minute fare 48 hours before departure than online travel agencies or travel search engines.

Booking hotels in the U.S.
Winner: Hotels.com

When to use it: Any time you’re shopping online for a hotel stay.

Why we like it: Hotels.com offers the best combination of rates and functionality of any site we tested. For instance, we found a marina-view room with breakfast at The Dana on Mission Bay in San Diego for $139 per night, $20 less than on Expedia, Orbitz, Quikbook, or Travelocity — or even the hotel’s own site. Sliding toolbars allow you to sort results by price, star ratings, and guest ratings.

Hotels.com has a “no change or cancel fees” policy, but it covers only charges levied by the site, not by the properties themselves. One of the most confusing aspects of selecting a hotel is the very subjective star ratings, since each site uses its own criteria. Hotels.com provides ratings based on reviews by the site’s “experts” and guest ratings based on customer surveys.

Tip: Hotels.com’s Rate Calendar has the best comprehensive pricing comparison six months out.

Caveat: The site has offerings worldwide, but Kayak and Asia-Hotels.com have more options for Asian properties.

Runner up: Orbitz.com's booking tools are just as useful as Hotels.com’s, but a few times Orbitz posted rates for sold-out rooms.

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