When booking online, you're often on your own.

That's the message we hear repeatedly from fellow travelers: When the room that looked great online turned out to be a dump; when you forgot and booked the rental car in your maiden name; when you booked a tour at a euro price when you thought it was dollars – you have no one to blame but yourself.

Linda Smith of Miami heeds that lesson. Though she has never been burned booking online, she's cautious. So when she found an unusually good deal for a New York hotel room next March at an unfamiliar booking site, she grabbed it. But she contacted us to find out how to vet the validity of a Web site.

A savvy consumer, Ms. Smith already had done what she could.

She carefully checked the booking rules, which allowed her to cancel without penalty until the day before check-in, a liberal policy.

She checked for professional memberships. The site claimed membership in organizations including the American Society of Travel Agents, though because the company does business under several names she had trouble verifying the membership.

She checked with the Manhattan Better Business Bureau and learned that the company has a satisfactory rating.She called the hotel and verified that it had her reservation. And she talked with her credit card company, which told her it would offer a credit if the room didn't exist at the last minute, even though the charge was made months earlier. (This isn't the case with all credit cards.)

"It's a terrible feeling – you could be in New York without a place to lay your head. Online, you don't know who you're dealing with," she says. "I won't know until March how it worked out."

Is the hassle worth it? For Ms. Smith, the answer is yes. She saved more than $125 per night.

About 29 percent of other leisure travelers agree. That's the percentage who booked last year via the Internet, for total sales of $86 billion, says Henry Harteveldt, vice president at Forrester Research, a firm that tracks travel trends.

But the Web isn't just about saving money. For the past decade, travelers have been able to research global trips, trade tips with other travelers and evaluate options easily, at whatever time of day or night they like.

Increasingly, technology helps them do it more easily. Some sites, usually those set up by an airline or hotel, offer talk-back options that enable you to speak with an agent in real time via the Internet.

Many have added e-mail newsletters and downloadable widgets that alert travelers about sales and price changes on trips that interest them. On some sites, for instance, "you can say, here's my budget, and they'll let you know when a fare that meets your budget is available," says Mr. Harteveldt.

One of the biggest additions of recent years: traveler reviews.

Since launching in 2000, Trip Advisor has racked up more than 10 million hotel reviews from 5 million registered members. With more than 25 million unique visitors monthly, Trip Advisor rates as the world's largest travel community, says spokesman Brooke Ferencsik. Though hotel reviews are the site's best-known feature, user-generated photos, videos and "go lists" (individual travelers' favorites) are growing.

The drawback: At Trip Advisor, anyone can post a review, whether they've stayed at the hotel or not and whether they're an experienced traveler or a novice.

Travel expert Pauline Frommer discovered the downside during a trip to Hawaii when she visited a hotel for her Pauline Frommer's Guides that didn't match the glowing reviews on Trip Advisor. After a negative review on the site, Ms. Frommer learned, the owner had encouraged friends and past guests to submit positive ones.

Hotel booking sites such as Quikbook, Expedia and Hotels.com also have added user reviews, but these offer an additional layer of security: Only travelers who have booked the hotel through their services can post opinions.

Qualified or not, such reviews can punch up business or smash it. Forrester's research indicates that 36 percent of travelers look at traveler rankings when choosing a hotel, and of those, 73 percent said those reviews affected their choice. Yet, only 29 percent of travelers have written reviews, says Mr. Harteveldt.

Interactivity isn't just about reviews, message boards and the sort of forums long popular on Lonely Planet and Cruise Critic.

Increasingly, the Web offers tools that enable travelers to get customized information for trip planning.

Mapping offered by sites such as Mapquest, Google Maps, Rand McNally and AAA has gone a step further with tools that find gas stations closest to the airport (at Expedia) and ones such as GasBuddy (www.gasbuddy.com) and Mapquest's gas-prices feature (http://gasprices .mapquest.com), which help you find cheap gasoline. AAA's Fuel Cost Calculator (www.fuelcostcalculator .com) will help figure out how much you're likely to spend on fuel during a trip.

And if you're looking for fuel of another sort, Pubwalk maps pub itineraries in more than 65 U.S. cities.

As groups of friends and family have hit the road together, sites such as Triphub, where group members can discuss plans, plot an itinerary and share maps, have become more popular.

Podcasts and mobile-enabled features also are growing. Cities such as Philadelphia (www.gophila.com) offer free podcast tours, while sites such as Priceline have added features that allow travelers with mobile devices (such as phones and PDAs) to check real-time hotel availability, then call directly to someone who can book the room.

Whether they feature the latest technology or not, the Web sites most useful for travelers are those that offer accurate, timely information that's easy to access.

That can include up-to-the-hour details on lines and delays at airports (Flightstats and Orbitz), forecasts about when airfares probably will be cheapest (Farecompare and Farecast), the best and worst seats on various airplanes (Seatguru), the price of winning bids on Priceline (http://biddingfortravel.com), alerts when airfares have dropped on tickets you've already bought (Yapta), locations of pet-friendly hotels (www.dogfriendly.com) and videos of hotel rooms in Europe (TVtrip).

So much information from so many sources may be overwhelming. One answer: Consult an expert.

Editorial publications such as Cruise Critic, Smarter Travel, World Hum, Hotel Chatter, Professional Travel Guide, and newspapers, magazines and guidebooks offer unbiased expert opinions online.

Many feature timely blogs, such as guidebook author Arthur Frommer's blog (www.frommers.com/blog); TravelMavens (www.travelmavens .net), run by the retired travel editor of the Cleveland Plain Dealer; and the Miami Herald's "Travels With Jane" (my blog) and "Exit Strategies," where travelers can post comments and ask questions.

And don't forget travel agents.

While few travelers these days will use an agent to book a simple air ticket to New York (an agent's fee may be $50), studies suggest that an increasing number of travelers are opting to shortcut the time-consuming Internet-booking process in favor of using agents, especially for complex itineraries and luxury trips. And as many as 90 percent of cruises are booked through agents.Booking sites compared, and more.