Adam Feinberg, a high school global studies teacher, posted the most documents of any New York City teacher onShareMyLesson.com, a new union social media website.

It was more than just altruism that drove Adam Feinberg to post hundreds of instructional materials online for his colleagues around the world to use. There was also, he hoped, a wedding gift waiting for him when he was done.

Feinberg, a global studies teacher at the Secondary School for Law in Brooklyn, was jockeying for a vacation prize that American Federation of Teachers offered to the teacher who posted the most documents toShareMyLesson.com, the union’s new curriculum-sharing website. Feinberg’s tally of over 300 worksheets, lesson plans, and slideshows won him $5,000 to pay for his European honeymoon.

The website, which the AFT launched in partnership with the British publishing company TSL Education last year, is part of a growing online ecosystem that has emerged in recent years as educators across the country confront the challenge of transitioning to new Common Core standards. Existing curriculum materials are not aligned to the new standards, which emphasis text skills, non-fiction, and critical thinking.

In New York, which made the controversial decision to roll out tests aligned to the new standards ahead of most states, education officials have spent $28 million to build EngageNY.org and pay nonprofit vendors to develop free curriculum materials that teachers can download.

In New York City, part of the $120 million price tag that officials often cite as an example of their investment Common Core preparation has gone towards paying teachers to develop curriculum materials for the Department of Education’s Common Core Library site.

Still, teachers are craving more.

“I go home and I start googling,” said Joe Negron, an eighth-grade math teacher at KIPP Infinity Middle School who spoke on a GothamSchools’ panel about Common Core this month. “I want to find a go-to place so I can spend my energy thinking about the how and not the what.”

Teachers struggled to build professional relationships and find appropriate curriculum materials long before the Common Core arrived. But several sites have surfaced to connect teachers to online resources — and each other — as they face the new standards even as the capacity for in-person professional development has not changed substantially.

The sites are getting a big boost from the philanthropic world, led by the Bill and Melinda Gates Foundation.

Negron and other math teachers said they often refer to IllustrativeMathematics.org, a site built and maintained by the University of Arizona with a $3.4 million grant from the Gates Foundation.

Another Gates-funded site, LiteracyDesignCollaborative.org, provides a template that allows teachers to plan units and tasks around the new learning standards regardless of the subject they teach. The new standards call for students to develop reading and writing skills not just in English classes, but in social studies, science, math, and technical subjects as well.

The video site TeachingChannel.org, which has received about $11.5 million from Gates and $500,000 from the Hewlett Foundation, posts professionally produced videos of educators sharing lessons, instructional strategies, and other work.

Then there are the social media sites that ShareMyLesson.com is competing with. The for-profitBetterLesson.com, which we wrote about in 2010 about a year after it launched, makes its money by forging partnerships with charter management organizations and school districts, whose teachers can share and exchange work in private networks. The Boston-based company received $1 million in seed money from the New Schools Venture Fund and has grown from 7,000 users to more than 65,000 users as of January 2012. It’s also picked up some major clients, including KIPP, Uncommon Schools, Rocketship Education, and the Los Angeles Unified School District.

ShareMyLesson.com is more populist, relying on its user base to develop and build the site’s content, which is free for all. It’s part social network, where teachers can find and connect around common interests, and part aggregator, allowing users to sort content by popularity, subject and grade level.

The site remains a work in progress. The quality and type of content varies widely, with little vetting of material that gets posted. One experienced teacher who reviewed the site said it could be “a great resource for new and novice teachers” but was less appealing for veterans.

The site now has more 218,000 registered users, 10 percent from New York State. Most of them aren’t active, however — just 60,000 of the site’s 260,000 documents have been uploaded by American teachers. Much of the rest comes from a similar website that TSL Education launched in 2008 for British educators.

The site does boast a small but growing library of math and English resources aligned to the Common Core standards, a base that UFT President Michael Mulgrew said he hopes to see grow.

“This is the start of what we want to be an amazing resource for teachers,” said UFT President Michael Mulgrew. To encourage teachers to contribute the site, the union has hosted training sessions, enticed teachers with more online contests, and even marketing it at press conferences.

Like so many other sites that are currently focused on developing core subject areas in the lower grades, ShareMyLesson has little high school content. And that’s the other reason Feinberg said he was driven to contribute to the site. As one of the site’s earliest active users, Feinberg said he rarely finds material that he can use for his own lessons.

“I actually don’t think I’ve ever found anything on there that’s been that useful,” said Feinberg, whose most popular document, a PowerPoint presentation called “How to Write a Thesis Statement,” which has been downloaded more than 400 times.

But Feinberg said he’s drawn by the site’s potential to become a hub for teachers to share and learn from one another. Having never taken a course on Chinese history, Feinberg said he’s often at a loss when introducing it to his students.

“Whenever I teach about that, a lot of is shooting into the dark,” Feinberg said. “There’s so much to know about Chinese history, [but] so many primary documents are in Mandarin or Cantonese.”

“So for me to not have any college-level expertise at my fingertips, that’s the kind of stuff that I think Share My Lesson can provide.”