Maybe you have a closetful of clothes you rarely wear. Or a garage stuffed with underused sports equipment. Or a garden shed packed with rusting tools. Come on, admit it—it's time to purge. But how do you get rid of unwanted stuff without being wasteful? Thanks to an Internet phenomenon known as the Freecycle Network (freecycle.org), doing so can be easier, and a lot more fun, than you might think. Founder Deron Beal had his brainstorm two years ago while working for a small nonprofit recycling organization in Tucson, Arizona. During his daily pickup rounds, Beal noticed that many businesses were also tossing out office supplies, telephones, even old computers. So he created a simple e-mail subscription list, signed up a few friends and members of other community groups, and posted items to give away—the first listing was for a queen-size bed—while encouraging others to claim anything they could use. By finding willing takers for others' castoffs, Beal hoped to not only help his neighbors but also keep useful items out of landfills. "I thought, 'If I give this a nifty name, it might just take off,'" he remembers.

The Tucson Freecycle list quickly mushroomed to its current roster of 5,400 members. Word spread, and soon Beal was helping set up similar groups in rural Minnesota counties, Colorado ski towns, Connecticut suburbs, and every major city in the country. He recruited a friend to preach the Freecycle gospel in Europe, where dozens of towns and cities inaugurated their own circles. Now under way in Argentina, Taiwan, Nigeria, and seemingly everywhere in between, Freecycling has a beachhead on all continents except Antarctica. About 100 more groups form each week. The largest in the world is in Portland, Oregon, with more than 19,000 members—3 percent of the entire city.

Though Freecycling has an immediately obvious draw (free stuff!), its enduring appeal often turns out to be more altruistic. Many group moderators, who volunteer their time to keep things running smoothly, say that while people may join hoping to get something for nothing, they usually discover equal, if not greater, joy in giving items away—especially when it's that never-used NordicTrack moldering in the basement.

Freecycle lists offer a fascinating, even addictive, glimpse into people's lives: their aspirations, abandoned hobbies, family woes, and guilty pleasures. During a single week in May, Freecyclers in New York's Hudson Valley were getting rid of three dozen self-help books, 500 diapers, two pieces of railroad track, a supply of canine multivitamins ("our dog passed away"), and "a dancing cucumber that sings, 'Oh, where is my hairbrush?'" Other members were in search of a functioning lawn mower, a dead computer ("I like to see if I can get broken stuff working again"), empty milk cartons for a craft project, a dehumidifier for a leaky apartment, Boy Scout uniforms, and an exercise bike. One person wrote, "I feel silly asking, but did anyone tape Desperate Housewives last night?"

Members have added their own twists on the original idea, with some announcing garage "sales" (no money is exchanged) and others holding "free-for-alls," group giveaways in a park or other public place. Sometimes a call goes out on a Freecycle list for, say, mothers or teachers to meet in a local coffee shop or hold a tailgate party to exchange outgrown baby clothes, toys, or school supplies. Freecyclers say that such off-line gatherings, as well as moderator exhortations to find a good home for your items (rather than always giving fast responders first dibs), foster a polite and grateful "gifting community" that feels more personal than getting your freebies from the newspaper classifieds.

At last count, 3,044 Freecycle groups with 1.6 million members worldwide were keeping at least 55 tons of stuff out of landfills every day. But success has come with complications. A few initial guidelines—"keep it free, legal, and appropriate for all ages" remains the most basic—have grown into a friendly but lengthy set of rules distributed to new members. Depending on the group, these may include no offering "of yourselves or your children," "no requests for illegal copies of software," or reminders about the risks of inviting strangers to your home. Most lists get so much traffic that members often opt to read messages on the Web sites instead of having their in-boxes flooded with offers and requests.

Beal sparked controversy among members earlier this year by accepting $130,000 in underwriting support from Waste Management, the largest garbage company in the United States. That corporate sponsorship, along with other internal disputes, has led the moderators of at least 30 local groups—including the gargantuan 13,000-member one in DallasÐFt. Worth—to split off and start their own small alternative networks.

Despite the organization's growing pains, there's no denying the increasing popularity—and influence—of the concept it pioneered. Taking note of the expanding ranks of Freecyclers, dozens of city and county waste-management programs now alert their customers to local groups. Curbside Incorporated, a company that manages household hazardous-waste disposal for 70 cities and towns in Colorado, California, and other states, gave away 7,000 pounds of used (but usable) paint, pool chemicals, and other products at its Denver facility in 2004. After it started advertising on the local Freecycle site at the beginning of this year, the company distributed 37,000 pounds of products in just eight months.

Freecyclers may also become something of a political force. In Tucson, their concerted outcry recently helped protect city grants to nonprofit community groups, including the local recycling organization that helped spawn Freecycling. Whether it's a "temperamental" toaster, a bag of books, or a helping hand, what goes around comes around.

Michelle Nijhuis writes about science and the environment from her home in western Colorado.

Illustration by Jon Cannell