Big City The Ids and Superegos of Brooklyn Mingle Online at Freecycle NYTimes.com

Some enterprising Brooklynite was clearly inspired on Friday afternoon to host a really good Memorial Day weekend barbecue — the best kind of barbecue, in fact, the kind someone else pays for.

“Need grill, charcoal, top-quality hamburgers, hot dogs, chicken (only breast) and steaks,” he posted on the Brooklyn forum of Freecycle.org, a site where people offer their unwanted goods free of charge and others request goods they’d like to own free of charge. “Also need fixings like chips, drinks, salads and other sides. Not to mention beach towels, blankets, folding chairs, etc.” (By “etc.,” perhaps he meant old friends, good times and a high of 72.)

It’s a big borough, and a big Freecycle community — almost 13,000 members in Brooklyn, compared with fewer than 3,000 in the Bronx. (There’s a citywide site, but none just for Manhattan.) So sure, it could happen. People replace grills, sometime right around Memorial Day — what do they do with the old ones?

Or one can easily imagine someone in Brooklyn Heights getting ready to leave town, feeling bad about some hamburgers — yes, top-quality hamburgers — that had been sitting in the fridge and now would never get eaten. Salvation and someone’s dream barbecue, just a few e-mail exchanges and subway stops away.

Someone has a fantasy; someone has a conscience. Freecycle is where the ids and the superegos of New York collide on a daily basis, usually with happy results. It’s a vehicle for extravagance or generosity, for small-scale Horatio Alger-style victories: microwaves, furniture, pianos, all available to anyone with access to a computer and a story convincing enough to beat out the other worthy competitors.

It’s also a reliable display of resourcefulness bordering on compulsion. From the last week or so: “Wanted. Manila folders (used O.K.). I can pick up anywhere close to transportation.” Or “Promised: Pentel refill erasers.” Or “Offer. A Lego set from the ’70s; not in best shape, though some do still fit.”

Some do still fit? Exactly how many are we talking?

Future anthropologists trying to determine the values of postmillennial New York could examine one week on Freecycle Brooklyn and glean volumes about the culture. (“Wanted. MP3 player. I am nothing without one!”) Such anthropologists will make what they will of a glut of Epson printers and aquariums, and unceasing demand for Snap-N-Go baby strollers.

Studying the borough, they might draw elaborate connections between the wheatgrass juicer and Darth Vader mask requested last week and the 100 journals of the National Association of Social Workers offered during the same time period.

But it’s as much the popularity of the site as its contents that says something about Freecycle Brooklyn, in particular. Its numbers reflect a certain (sometimes self-conscious) pride in community, combined with a D.I.Y. aesthetic in which frugality, eco-consciousness and creativity merge or are merely mistaken for each other, depending on the perspective. There are more a few hundred more Freecyclers in Brooklyn than in all of Los Angeles, which seems entirely predictable.

Among the Brooklyn postings lie hidden snips of poetry: “Please contact me if you have something small, bright and yellow.” An artist working on an installation posted that cry for help.

All over Brooklyn, one can imagine people looking up from their desks to notice a pencil, a stray magnet, an oversize button, all small, bright and yellow, no longer mere detritus, suddenly all creative inspiration. Intended or not, her installation is more like performance art, making unwitting artistic collaborators out of volunteers.

Someone logging on in hopes of snaring one of those hot Snap-N-Gos might easily get hooked into a regular habit, scouring the borough’s Freecycle site not for a free air-conditioner, but for its telegraphic tales of the city: the new bicycle messenger who’s desperate to find a bike before his first day of work in just a few days; or the woman willing to travel across the borough for a pair of used running sneakers, preferably not too used; or someone seeking, mysteriously, any and every possible hair product, including but not limited to pomade.

At 10 minutes to midnight on Thursday, 12 cans of Glowmaster butane fuel were offered for the taking. By 8:10 the next morning, they’d been fought for, divvied, the news of their new ownership already posted. Desire, competition — they never rest.

The neighborhood yard sales that pop up all Memorial Day weekend are social, and have the promise of serendipity, but are ultimately inefficient. Freecycle offers New Yorkers the feel-good values of the Park Slope co-op or some thrifty grandmother, but at stock-exchange speed.

Want.

Offer.

Promise.

Could any three words be more New York than that?

E-mail: susan.dominus@nytimes.com