When planning the first of what would ultimately be more than 20 trips to the Sahara Desert, Brit Chris Scott was drawn by "the challenge of being completely self-sufficient in one of the world's harshest wildernesses." Scott, who made his first Sahara crossing alone on a motorcycle—3,000 miles (4,828 kilometers) through Algeria and Niger—at the age of 21, was terrified of wrecking his bike in the middle of the largest desert on Earth, where it rains only a couple of times a year and daytime temperatures can top 130ºF. For him, though, the thrill of a totally self-supported trip along ancient camel caravan routes outweighed any danger or discomfort.

In 2000 Scott wrote Sahara Overland (Trailblazer Guides, $30), which advises travelers to choose a route wisely (the two-week Atlantic journey through Morocco, Mauritania, and Senegal is safer, though less dramatic, than the three-week inland route through Algeria and Niger), to closely monitor news from the region (www.horizonsunlimited.com/bulletin is a good source), and to prepare for last-minute rule and route changes. For instance, Algeria and Libya currently require travelers to be accompanied by a government-vetted guide ($180 a day), and last year a spate of well-publicized abductions have steered most tourists clear of Algeria; next year a brewing Tuareg rebellion may make Niger a no-go.

Several companies run guided jeep tours across the desert (try www.highandwild.co.uk), though the classic (and cheapest) route is to hook up with a European traveler who has a vehicle and an extra seat (check www.sahara-overland.com). If you want to play head navigator, you'll need to buy and outfit a vehicle in Europe and ferry it across the Mediterranean ($600 and up for the crossing; see www.sncm.fr). Once you've dealt with the logistics, a few weeks in the Sahara is a liberating experience. "You're overwhelmed," says Scott, "sometimes by your own vulnerability, sometimes by the stars, sometimes by the friendliness and generosity of the nomadic people you meet."

Three years ago, Sally Fenton didn't even own a bike. Last summer, the 57-year-old rode 3,600 miles (5,794 kilometers) in 60 days, crossing the continent from San Diego to St. Augustine, Florida. "To get up at 6 a.m. and know that all I had to do that day was ride a bike, with the sun on my back and the wind in my face, that was priceless," says Fenton. "I never had to go inside." A self-contained coast-to-coast backroads tour is a dream shared by many, if not most, serious road bikers. "I nursed visions of this for several years," says Bunni Zimberoff, who made her first of two cross-country trips in 1996. "The biggest problem, of course, is creating a two-month window in a busy life."

Zimberoff began watching the "companions wanted" columns in cycling magazines and found a female partner who looked like a good match. Though the Adventure Cycling Association (ACA) recommends that cross-country riders start training seriously at least four months before departure and work up to riding a full-day's mileage with a full load of gear by two weeks before the start date (www.adventurecycling.org offers detailed training regimens), Zimberoff started just ten weeks before her trip, gradually filling her panniers with more and more books and riding longer distances. "The first week of the trip is essentially shakedown time," she says. "The days are short and some of the early climbs are walked, but within a week or so you are acclimatized to the load and the work."

Use the ACA's maps ($11 each; about $100 for a cross-country set) to stitch together a low-traffic route through scenic terrain. The ACA offers a guided 93-day trip for $3,600 (about $39 a day), though if you go solo and camp and cook your own food, you could spend as little as $10 a day. When packing, bring along as little as you can get away with; aim for 30 pounds (14 kilograms), and don't consider exceeding 45 (20 kilograms). Zimberoff's single most critical item: a variable-size sink drain plug for doing laundry in budget motels and campgrounds. "It costs little, weighs less, and makes a tremendous difference in the trip."

"This is the warm baby pool of sailing adventures," says Olga Katsnelson, a New Yorker and amateur sailor who rented a crew-free 45-foot (14-meter) catamaran with seven friends and spent a week exploring the British Virgin Islands. "You're on your own, going where you want to go. But if you do get into a jam, you call the company on the radio and say, 'Uh, help, I spilled my coffee.' They come right out." The calm waters of the Virgin Islands are a prime choice for first-time bareboaters, though Baja, Belize, the Mediterranean—even the South Pacific—are all viable options. Sailboat charter companies generally don't require formal sailing certification, but at least one member of your party should have significant experience with the class of boat you want to use. (Most companies will have the potential renter submit a "sailing résumé" via their Web site.) Beginners can take lessons through American Sailing Association-affiliated schools (www.asa.com). If you just need to brush up on your skills, most charter companies will send a captain out with you for a few hours to lead you through boat and chart briefings and help you gain confidence at the helm.

With a group of six sailors, your weeklong tropical vacation will set you back as little as $450 apiece (excluding airfare). In the Caribbean, contact Bareboats BVI ($2,795 and up per week; www.bareboatsbvi.com) or Sunsail ($2,660 and up per week; www.sunsail.com). The Moorings ($2,765 per week in the B.V.I.; www.moorings.com) charters boats out of the Caribbean, the Seychelles, Tahiti, and Tonga.

From the print edition, October 2004

What It Takes: The best dream adventures you can make happen—today

Welcome to the Neighborhood: Can mountain lions and mountain bikers get along?

Secrets of the Black Hills: Granite towers, sunken caves, and singletrack abound

Pelton's World: Five things travel guidebooks never tell you