PHILADELPHIA — In a funky corner of this sprawling city, a sisterhood of a traveling black dress is forming.

First, Dara Patrusky picked up the Ted Baker halter dress from a Buffalo Exchange thrift store (it still had the tags). Then she passed it on to her friend, Naomi Brownstein. Now, Brownstein has brought it here to the Bohema boutique, where Patrusky, in a twin nod to spring-cleaning season and Earth Day, is hosting her latest clothes swap and where Brownstein hopes the frock finds a new and grateful owner.

"That's the beauty of the swap," says Brownstein, 59, a paralegal, as a dozen women, some with plastic glasses of wine in one hand and reusable Trader Joe's bags on their shoulders, rummage through each other's sweaters, bags, shoes and coats: One woman's castoff is another woman's catch.

When it comes to freshening their — and their kids' and husbands' — wardrobes, more women are exchanging shopping for swapping. Friends are gathering at homes to trade gently worn treasures (and gossip); strangers are exchanging stuff through online swap sites or at organized meet-ups like Patrusky's, sometimes with DJs, massages, hair and makeup consultations and a full bar thrown in. Leftover loot gets donated to charity.

But it's not just togs that are getting traded. DVDs, video games, paperbacks, housewares, unopened toiletries, unopened energy bars, even unused bellybutton rings: If it might have otherwise languished in a basement, closet, cabinet or drawer — or ended up at Goodwill in exchange for a teensy tax deduction — it's ripe for swapping.

The rise of the quid pro quo possession comes courtesy of a host of reasons: budget-tightening during a persistently sour economy (swapping is mostly free, save for shipping costs or, for face-to-face fetes, a nominal entry fee); eBay, consignment-store and yard-sale fatigue (you might only get a few dollars for all the effort required); hand-me-down headaches (rifling through a garbage bag of kids' clothes is daunting and inefficient); environmental awareness (swapping, of course, is the ultimate form of recycling) and fashion experimentation (it's a frugal way to try out trends).

Frugal and fun

And in the case of offline swaps, it's a way to return shopping to its social sport roots. "Traditional shopping has become a chore," says Marshal Cohen of The NPD Group, a market research firm. Swap parties, like direct-sales parties for jewelry and makeup, turn the goods-gathering experience into "shopertainment — what stores should be doing but aren't." That's why the cash-flush, as well as the cash-strapped, partake: Who can resist stumbling upon a new (to you) Nanette Lepore cocktail dress, picked up along with a networking tip, both gratis?

There's the same high as standard bargain hunting with "none of the guilt," says Melissa Massello, co-founder of The Swapaholics, which has been staging 250- to 300-person monthly clothing swaps in auditoriums, school gyms and warehouse spaces in the Boston area and Worcester, Mass., for just over a year. Due to high demand, they're expecting to expand soon to weekly events. A definite "giddiness" pervades the experience, says Massello, 31, who counts a brown leather new-with-tags See by Chloe jacket as one of the top fruits of her trawls. "It gets crazy." Women, including a group of 50 to 60 diehards, line up in advance, their noses pressed to the windows in hopes of sneaking a peek at the pre-sorted, hanging goods racked according to category, from denim to dresses.

At most in-person, large volume swaps, participants drop off clothes in advance or at the start, and nobody knows who donated what (unless they cop to it). What's next is a free-for-all: Attendees stuff as much as they can fit into shopping or garbage bags — no matter if they only donated Old Navy but then snagged Calvin Klein. And if you only bring one T-shirt but leave with 10 handbags, no one's necessarily keeping score.

"Imagine the Running of the Brides at Filene's Basement. That's what it's like when we open doors to the swap — no exaggeration," Massello says.

The addiction extends online. Michele Thompson, for instance, has participated in more than 125 swaps through SwapMamas.com — in nine months. "I'm on a first-name basis with the postman," confesses Thompson, 27, a college student and mother of two boys in Odessa, Texas. By posting pictures and lists of what she has to give and what she hopes to receive, she recently snagged a Samsung camcorder from Columbia, Mo., in exchange for a 60-count box of size 5 diapers that her littlest one, Zander, was growing out of and a half-dozen pieces of 2T clothing. But Thompson scored easily her most coveted keeper last winter: a 1.5 total carat weight diamond wedding ring set first purchased for $2,000 that eerily matched the one stolen during a Grand Cayman vacation in 2005. The original owner, from Philadelphia, Tenn., was going through a divorce and as a newly single mom had needs vs. wants. Thompson came through with a "huge" box (it cost $80 to ship) of an entire 3T boys' wardrobe, from pj's to swim trunks to shoes boasting labels like Ralph Lauren and Mini Boden. The clothes were hand-me-downs from her older son, Jaiden, intended for Zander, "but for something like this, Mommy had to make a decision." Of course, it's tough to police a virtual community created on trust. On occasion, a swap can turn into a dead-end street.

Last summer, Brooke Remillard of Lawrenceville, Ga., sent a "whole bunch" of cloth diapers to a fellow Southerner and in return got an empty mailbox. (The miscreant mom was asked to cancel her SwapMama account.) But in nearly 250 transactions over eight months, that's been the part-time jewelry designer's only swap snafu. "Honestly, I think there's so much more good," says Remillard, 26.

Darcy Cruwys founded SwapMamas last year originally as a baby-gear exchange, but quickly the now-7,000 members started bartering "things I hadn't even thought of": Wedding china for clothes, a "gorgeous" Burberry trench coat for maybe 20 cloth diapers. "It's all really across the board. They just figure out what's fair among themselves," says Cruwys, 41, of Bozeman, Mont., who focused her energies on the free site, which she says garners more than 20,000 unique visitors a month, after she was laid off last year. "It's about more than stuff," she stresses. "It's about just helping one another out."

A growing trend

And goodness knows, we're wallowing in stuff: about 23.8 billion pounds of clothing and textiles land in landfills every year, according to Goodwill. Another new swap site, ThredUp, did further digging and in surveys conducted last year found that a quarter of a person's closet goes unworn and that by age 17, kids have outgrown more than 1,300 articles of clothing.

ThredUp's men's and women's shirt-swapping service started in September and now numbers around 10,000 swappers — about 55 percent guys. Marc Hofner, a user for the past six months, has been "pretty impressed" with the shirts he's received. One piece, a striped white shirt, "just wasn't me," says Hofner, 30, a software engineer from Cambridge, Mass. No matter: "My intention is just to send it right back into the ThredUp system and trade up again."

The company's new kids' version has reached 3,500 members since it launched April 12. Cambridge, Mass.-based co-founder and CEO James Reinhart has a hunch as to what's behind the sudden popularity: "Having to go and buy a whole new season of stuff for a toddler feels a little more painful now than it probably did five years ago."

Likewise, splurging on something relatively frivolous seems almost unconscionable to the women browsing at Bohema.

"It's such a sin that we spend all this money," says Jennifer Cybulski, surveying the plastic bins. Cybulski, 32, a dancer and Pilates instructor, is eyeing a crimson cardigan. "It's Ann Taylor and (per the stapled-on tag) it's dry-cleaned, so that means someone took care of it," she says. Swap etiquette, whether spelled out or unwritten, depending on the event, forbids anything holey, torn or stained. "Share your finds," encourages Patrusky, 48, shepherding her 10th or so swap (she's dance fitness instructor by day; this is largely a hobby). "It's not like going to the store because people aren't trying to sell you stuff." The only real cost here is the $5 admission.

Indeed, the atmosphere is more courteous than competitive. When college student Julianne Weingart walks out of the dressing room wearing a sleeveless sea-foam dress, a chorus of "That's really cute on you!" rings out. Weingart, 21, is sold.

"I usually take stuff to the Salvation Army," says Garland Nelson, 27. "But this is more of a thrill because you get to take something back with you," like a beautifully broken-in saddle leather Coach briefcase, with which as a saleswoman she'll tote her carpet and flooring samples. The price? A blazer and a tank top.