I-to-I Runs solid projects catering to gap-year students. It was bought by Tui Travel, one of the world’s largest travel companies, in 2009, so profit is a priority.

Earthwatch Sets the gold standard for voluntourism, with projects that often focus on scientific research and wildlife conservation and emphasize education for the traveler.

Global Volunteers Founded in 1984 by a young, idealistic American couple, this nonprofit organization runs community projects all over the world.

Habitat for Humanity Provides a perfect introductory voluntourism experience, though in some places the home building might be better done by locals. Participants are well taken care of, and the organization contributes money to the local economy.

Global Vision International Runs 100 programs, partnering with local groups in 25 countries, ranging from the Jane Goodall Institute to Rainforest Concern.

The Fuller Center for Housing's Global Builders Takes groups of volunteers for a week or two at a time to construct homes in 11 countries around the world.

I’m uncomfortable. I tell Castel she doesn’t need to keep thanking me. I speak French, but the other volunteers communicate only through smiles and sign language, underscoring my sense that we are alien angels swooping in to help. I am embarrassed that my work is so negligible: I sift sand at half the speed of the Haitians, and my hammering skills are laughable. Wouldn’t it be better, I wonder, if we had just sent money so Grace could hire an all-Haitian crew to build these houses? Aren’t we perpetuating the “white man coming to save us” dependency that has characterized Haiti’s relationship with America ever since the United States occupied the country in 1915? (The occupation ended in 1934, but the United States, for better or worse, has been deeply involved in Haiti ever since.)

A year ago, when I came to Haiti to take a look at post-earthquake recovery efforts, the country was still in crisis mode. Mountains of rubble and garbage filled the capital’s dusty streets. Downtown Port-au-Prince had become a wasteland inhabited by poor people still living in filthy, unsafe tent camps, while the big NGOs and the UN operated across town, near the airport, and the rich—as always—looked down on it all from the leafy, relative comfort of Pétion-Ville, up on the hill.

Humanitarian workers at local NGOs complained about how little had been done, despite the $15 billion that had been pledged by foreign governments and organizations. By some counts, more than 15,000 international NGOs had flocked to Haiti, yet it was hard for me to see much positive change.

A year later, I still wanted to help. I had heard aid workers grumbling disdainfully about what they called the “matching-T-shirt brigades” of condescending and insensitive volunteers, often Christian groups, pouring in to spend a week at a time “working” in orphanages, building homes, and handing out Bibles—but making little real difference.

Voluntourism has become a global business, fueled by a growing desire among travelers to take meaningful trips and try to do some good. Scores of companies offer travelers the opportunity to do everything from count and monitor wildlife to teach in schools. As voluntourism has taken off, experts have started questioning its merits—even suggesting that volunteering can cause more harm than good. “To be honest, I have never really felt like I truly helped anyone,” says Alexia Nestora, a former employee of the voluntourism company I-to-I, who blogs as Voluntourism Gal. She adds that voluntourism can be a good thing if you go in knowing that you aren’t going to “save” anybody.

Real development, beyond delivering emergency supplies, requires a deep understanding of culture and issues on the ground, which big international organizations often lack. So how, I wondered, can travelers help? I decided to return to Haiti to see for myself what difference volunteering could make. On my flight down, I bumped into one of the matching-T-shirt groups I’d heard about, young people from a church in Georgia dressed in red shirts emblazoned with the words helping haiti. “Do you think we’ll see any of that creepy voodoo stuff and satanism?” I heard one of them ask.