It’s Black Friday. Instead of shopping, why not yerdle?

Yerdle is a sharing and shopping website and mobile app being launched today by two stalwarts of corporate sustainability — Adam Werbach, the former Sierra Club leader and Saatch & Saatchi marketing guy, and Andy Ruben, Walmart’s first sustainability director.

Andy and Adam, who are both 39 and live in San Francisco (natch), have come up with a very cool idea. Yerdle is a way for people who have stuff to give away, or other stuff they want, to share with one another–before heading out to the store to buy something new. By today, after a beta test in the Bay Area, they expect that more than 10,000 items will be offered on Yerdle.

I took a sneak peek at the site the other day and found, among other things, a Ikea children’s table and chairs, a yoga DVD, Sesame Street DVDs, red Baby Gap sweats, a dustbuster, a radio alarm clock, a laptop sleeve, a pasta maker, kids books, a collection of little wooden dress-up dolls, and more–and that’s before inviting my friends to join.

“Why not shop from your friends’ attics and garages and sporting closets before going to the store?” said Andy when we spoke the other day. He said the idea for the site came to him when he had to equip his five-year-old daughter for her first soccer game and realized that lots of girls on a nearby field had probably just outgrown the clothing and equipment that she needed.

Said Adam: “If you need a tent, a circular saw, kids soccer cleats, or thousands of other items that you only use sporadically, try sharing through yerdle. Saving money doesn’t suck.”

As Andy and Adam have tracked environmental and business issues, they’ve been encouraged and disappointed by what’s they’ve seen. “We’ve been incredibly proud of what’s happening–sustainability is becoming mainstream–and incredibly frustrated by the pace of change,” Adam told me.  Businesses like Yerdle that promote sharing, he said, are the next phase of sustainability.

I’ll spare you a lecture about overconsumption but whenever I go to a mall at this time of year (which is almost never) I can’t help thinking that people are buying stuff they don’t need with money they don’t have–and that, worst of all, all this crazy shopping  is unlikely to add to our collective happiness. It’s time to get off the hedonic treadmill, friends, and rediscover the values of frugality and community.

What sets Yerdle apart from well-established websites like FreeCyle and Craigslist is that it connects people with their friends, typically through Facebook. People also will be able to organize around workplaces, churches or synagogues, or the schools that their kids attend which, as practical matter, will make it easier to exchange things. The site will also offer a robust mobile platform, the founders say.

Yerdle isn’t a non-profit, though. Its business will depend not on sharing but, yes, on shopping. If you are seeking a bike or a Cuisinart or a ski jacket and your friends are not offering one, Yerdle will send you to a merchant–Amazon, say, or Walmart, or retailers with a commitment to sustainability, like Patagonia, to find what you need. It will collect a commission on all those transactions. In theory, at least, this will take some of the guilt out of shopping–you’ll feel better about buying something new if you have tried at first to get it via sharing.

Partnerships with retailers and brands will open up interesting possibilities. What if, every time I buy a book from Amazon (my shopping addiction), Yerdle kept track of my purchases? Then, when I’m done with the book, I could click to make it available to a friend.

Adam Werbach and Andy Ruben

Adam and Andy told me they are raising about $750,000 to get Yerdle going, and they’re about halfway there, with most coming from friends and family. Among the early backers are Lisa Gansky, author of The Mesh, which is all about sharing businesses, tech investor Andy Rappaport of August Capital and Mark Pincus, the co-founder of Zynga. They’ve turned to sustainability gurus Bill McDonough and Paul Hawken for advice on their startup.

Will Yerdle catch on? I still a lot of potential but some obvious drawbacks. People will be reluctant to give away items with real value that could just as easily be sold on Craigslist or eBay. Shipping will be an issue. I have a treadmill in my basement that gets very little use, but giving to a friend is easier said than done. What’s more, I like the idea of giving things to people who need them, as opposed to my friends who are, for the most part, financially quite comfortable. Having said that, I’ll give Yerdle a try. It’s sure to be more pleasant than a trip to the mall or Walmart.

Speaking of which, I asked Andy, who spent a decade at Walmart, whether he now feels like a traitor to the retail industry–which, after all, is driven by the goal of selling people as much stuff as possible, whether they need it or not.

Not at all, Andy replied. “In every generation of retail, the model evolves, based on better serving customers,” he said. “The discounters have only been around for about 60 years. I hope we accelerate a trend in retail that creates even more value for customers. We’re at the beginning of the next great model in retail.”

We’ll see about that. But there’s no doubt that he’s just made a jump from the world’s biggest company to one of its smallest.

Here’s a video about Yerdle by environmentalist (and Sunday school teacher) Bill McKibben, who some years ago wrote a book called Hundred Dollar Holiday: The Case For A More Joyful Christmas: