LinkedIn, the social network for job hunters and professionals, is expanding once more in the nonprofit space.

The site recently added a “volunteer marketplace” where members can search posted opportunities to volunteer in their communities. LinkedIn will also suggest volunteer matches in members’ “Jobs You May Be Interested In” e-mails.

Some recent postings sought a human relations strategist for a group working with low-­income youths, a grant writer for an organization that provides support services to people in Haiti and a board member for a group that helps single mothers.

LinkedIn, which has 250 million members, usually charges companies a fee to post job opportunities, costing up to $400 for 30 days.

But nonprofit organizations posting opportunities through the new marketplace will receive a 90 percent discount, the company said. LinkedIn officials say the company will use those proceeds to give grants to its nonprofit partners. Organizations have to be registered as a 501(c)(3) in the United States to post because the new platform is first being tested domestically.

LinkedIn says it hopes to capitalize on the growing interest that people in the workplace have for causes.

“The number of professionals interested in using their skills to change the world outweighs the skills and opportunities available on the nonprofit side,” said Meg Garlinghouse, head of the company’s LinkedIn for Good foundation. “There hasn’t been a very efficient platform to do that. We feel like we are well-positioned to do that.”

Several nonprofits in the Washington region are using the new feature, including housing advocacy groups such as Rebuilding Together and Arlington Home Ownership Made Easier, the abortion-rights group Choice USA, the veterans organization Hire Our Heroes, the job skills group America’s Future Workforce and Atlas Corps, an international leadership group.

“We are looking for some help in creating press material for our Web site, and we haven’t had the expertise or time to do it,” said Kate Londen, communications manager at Choice USA. “The outside expertise is something we’ve always wanted to have.”

LinkedIn’s new do-good platform has been years in the making. The social networking site started its charitable arm, Linked­In for Good, in 2010.

In 2011, it added a volunteer and causes section to member profile pages, which 3 million members have utilized. Noting the interest, the company introduced Board Member Connect, a program that allows nonprofits to search for professionals who indicated they wanted to serve on a board. For the past six months, the company has piloted the volunteer matching concept and found what it considered to be notable success stories of perfect matches.

The concept of connecting business professionals to causes is not a new one.

Taproot Foundation of San Francisco brokers partnerships and pro bono projects between companies and nonprofits. Catchafire is a New York group that helps people design projects for charity. BoardSource, of the District, focuses on building nonprofit boards. Compass, another organization in the District, connects MBA graduates with nonprofit pro bono opportunities. And VolunteerMatch, also of the District, helps people find local causes.

Each acts as a third party to match professional skills with community groups. LinkedIn has partnered and consulted with some of these organizations to design the new platform and help nonprofits post opportunities.

Taproot knows the new Linked­In feature might replace some of its services, but it hopes the matching program will stir a wave of volunteerism in all workplaces.

“A mission-focused organization like ours, our hope is that more nonprofits have access to the pro bono they need,” said Lindsay Firestone, director of advisory services for Taproot. “Whether through our program or elsewhere, it’s a win.”

Capital Business is The Washington Post’s weekly publication focusing on the greater Washington business community.