Should you buy your airline ticket now or wait because the price may drop? Is there a better coach seat on your overnight flight than the one you've been assigned? How long will it take to walk from your hotel or cruise-ship dock to the sights and restaurants on your itinerary? Just a few years ago, finding the answers to these questions would have required a lot of time and help from a human being with more information than you—a travel agent, concierge, or personal assistant. Now, it's available in an instant, thanks to magic tools—some of them new, others tried-and-true, all of them on the Web, and most of them free.

AirfareWatchdog.com
The real live human-being fare wonks behind AirfareWatchdog find low fares that automated airfare search engines may miss. The result: a list that includes unadvertised sales and promo-code fares (AirfareWatchdog tells you which codes to use). Sign up for e-mail alerts for low fares from your home airport, as well as "to a city" alerts that list fares from various airports to your destination. Say you want to fly from Houston to Kona, Hawaii. The Houston-Kona fare might be $800, whereas the Dallas-Kona one might be $350. If you'd signed up to see all the fares to Kona, you'd know to combine the Dallas-Kona fare with a cheap Houston-Dallas ticket.

AutoSlash.com
Seeking the best price for a car rental? It's tough if you haven't got time to check back every so often to see if rates have dropped or to sort through all the rental-car discount coupons you get in the mail (often from airline loyalty programs). Luckily, Auto­Slash does this for you. It searches for the lowest rates, using all manner of publicly available discounts in its search (you needn't know any promo codes; it enters them for you), and once you've booked, keeps repricing your rental automatically. If the rate drops, it alerts you so you can rebook at the lower price.

AwardWallet.com
Don't be a victim of expiring airline miles or hotel points. AwardWallet shows you your point balances and expiration dates on one page, saving you from having to log on to a bunch of different airline and hotel sites every time you want to check your info. I use AwardWallet to keep track of all my family members' programs in one spot. (When anyone's miles are close to expiring, I prevent that from happening by making an online purchase from one of the hundreds of stores in that carrier's online shopping mall.)

Bing.com/travel
Want to know if you should buy your airline ticket now or wait? Or if the hotel rate you've found represents a good deal? Bing mines historical data to advise whether the fare you've found is predicted to rise or drop and whether or not a hotel's rate is favorable compared with its rates in the past for similar time periods.

BookYourAward.com
Tearing your hair out trying to use your frequent-flier miles or credit-card points for international flights in first or business class? Here's the help you didn't think existed. Gary Leff, the mileage magician behind Book­YourAward, knows all the tricks for getting you where you want to go for as few miles as possible, and he'll find and book your flights for you. For example, when a Condé Nast Traveler colleague wanted to apply her American Airlines miles to a flight to Bali in business class, it was going to cost her 210,000 miles. Leff found her the seats she wanted for only 122,500 miles, with the return portion from Hong Kong to JFK in Cathay Pacific's first class. His fee is $250 for two tickets traveling on the same itinerary.

Earth.google.com
When I'm weighing the pros and cons of one hotel or rental home versus another and I want to get a sense of their immediate surroundings, I rely on Google Earth. Before I rented a villa in Hawaii, for example, I consulted the site and was able to see that it was perfectly situated in the middle of a lava field, far from other buildings and only a few yards from the ocean. I've also used it to suss out cruise ports. Say I plan to be on a ship that will stop in Civitavecchia, the port closest to Rome. I'll turn to Google Earth to get a sense of how far the train station is from where the ship will dock.

EVReward.com
You're savvy enough to know that you can earn a ton of miles or points by shopping online from the stores in your preferred airlines' online mileage malls (which include everything from Target to the Apple Store). But were you aware that you can instantly find out how many miles each reward program is offering for purchases from the stores you plan to buy from? When I need to send a Harry & David gift basket, for instance, I'll punch "Harry & David" into EVReward; I may find that Delta is offering only two miles per dollar, whereas Continental will give me five.

FareCompare.com
FareCompare's trip alerts notify you when fares drop on the routes you're interested in. Because these alerts go out by e-mail several hours before the reduced fares are loaded into the airlines' reservations systems, you can nab the discounted seats before others do. You can request alerts for cities, countries, continents, carriers, classes of service, and specific dates.

HopStop.com
Trying to make step-by-step plans for city sightseeing? HopStop tells you how to get from point A to point B—on foot or by subway, bus, or taxi—and how long it will take. Use it if you're organizing a visit to Paris and want to know how much time to allow for a walk from your hotel in St-Germain-des-Prés to the Musée d'Orsay, and from there to the Marais, so you can gauge when to make lunch reservations.

ITASoftware.com
This airfare search engine provides a more comprehensive and unbiased list of flight options than online travel agencies do, making it easy to find the itinerary that represents the best combination of low price, good routing, and convenient schedule (another plus: Fares include all taxes). I use ITASoftware to choose the most suitable flight option, then go to the airline's Web site to book. ITA can tell you the cheapest days to travel to your destination within any given month. It also lists what events will be happening—concerts, festivals, exhibits—so you can plan accordingly. One caveat: ITA does not list certain low-fare carriers, including Southwest (which is why you also need WhichBudget.com, below).

SeatExpert.com and SeatGuru.com
It used to be that you had to know the model of aircraft you'd be flying if you wanted to pull up its seat map and learn the pros and cons of each seat as well as of the aircraft. Now, all you need is your airline and flight number. Plug these into both SeatExpert and SeatGuru before accepting a seat assignment or to find out whether you should try to switch seats and which to switch to if your seat has already been assigned.

TripIt.com
TripIt organizes your electronic travel reservations into one master itinerary. When you receive a confirmation e-mail—for a flight, hotel, rental car, dinner reservation, show, or event—forward it to TripIt and the site will consolidate all of your plans into an itinerary that fills in many blanks, adding links to online check-in, flight status updates, seat advice, maps, directions, and more.

WhichBudget.com
Want to know which low-fare carriers fly between two particular cities? Plug the cities into WhichBudget and the answer is yours. This tool can save you a bundle if you're headed overseas to multiple destinations and want to combine an open-jaw ticket to and from the United States with regional low-fare flights overseas. Say you need to fly from New York to Barcelona to Berlin and back to New York. WhichBudget will tell you that the Barcelona-Berlin route is flown by Air Berlin, EasyJet, and GermanWings. Depending on your travel dates, a JFK-Barcelona-Berlin-JFK itinerary could cost you $1,300 more than an open-jaw to Barcelona and back from Berlin combined with a Barcelona-Berlin one-way.

Yapta.com
When I need a specific flight on a specific date more than four months into the future—before any big fare sales have begun—I punch the details into Yapta, which then alerts me by e-mail when the price drops. In the rare circumstance that I must buy my ticket way in advance, before the sales have begun (say, if I've booked a cruise and must lock in the flights), Yapta will alert me to any price drop that exceeds the amount of the ticket-change fee, so I can contact the airline and claim a voucher for the price difference minus the change fee.

Zoombu.com
Trying to get from anywhere in the United Kingdom to anywhere on the Continent? Zoombu provides you with three detailed door-to-door route options—the cheapest, the fastest, and the greenest—that include modes of transportation, travel time, and cost. Say you want to know your choices for getting from London to Rouen in Normandy. Depending on your travel dates, Zoombu might advise that your cheapest option is a combination of trains, subway, and Eurotunnel that will take 12 hours and cost $179; your fastest option, a mix of taxis and the Eurostar, will take four hours and cost $737; and your greenest option—via subway, Eurostar, and taxi—will take 12 hours and cost $282.