Hands Up Holidays
This for-profit operator is for those are looking to add some volunteering to a luxury vacation. Travelers choose trips—which emphasize environmental sustainability and education—according to activity and comfort level (handsupholidays.com)
Visit game reserves in Botswana, staying at luxury lodges, and then volunteer for four days in the garden of a school in the Okavango Delta.

Hard-Core Trips
Amizade
Educational tourism is the focus of trips organized by this nonprofit operator. Groups stay in youth hostel-type accommodations (amizade.org)
Learn about the peace process in Northern Ireland while working with young Catholics and Protestants, then tour Belfast and Ireland's countryside.

Cross-Cultural Solutions
Founded in 1995, this nonprofit is for volunteers ready to make a time commitment of from two to twelve weeks. CCS partners with grassroots organizations in twelve countries. The bulk of the fees cover the cost of the trip rather than providing a direct donation to community projects (crossculturalsolutions.org) Spend three to twelve weeks in Dharamsala, India, teaching English or caring for the disabled.

Earthwatch
This thirty-seven-year-old nonprofit organization believes that work on scientific projects turns travelers into ambassadors for the planet. Travelers can help scientists with data collection in nearly forty countries. Housing is usually basic (earthwatch.org)
Spend a week gath-ering geological information on volcanoes in Costa Rica.

Globe Aware
A nonprofit, it offers short-term volunteer vacations for travelers who are willing to forsake luxury to discover a local culture (globeaware.org)
Work for a week with monks in Thailand, in a nursery, teaching En-glish, or doing emergency relief. Volunteers live with local families (no hot water).

Global Vision International
This for-profit operates almost like a charity: In 2007, seventy percent of volunteers' fees went to projects in the field. It has programs lasting from one week to one year for people who aren't looking for a relaxing holiday. GVI lists skill requirements and offers language classes (gvi.co.uk)
Do field research with an Ecuadoran conservation foundation to help protect the rain forests. Volunteers live in dorms.

I-to-I
I-to-I is one of the largest for-profit voluntourism operators in the world. As such, it is highly scrutinized, and sometimes criticized, by consumers and other voluntourism entities. Some students have argued that fees, which don't go to local communities, are inflated. The company emphasizes that fees cover trip and research costs, and encourages travelers to donate to the I-to-I Foundation, which provides funding to partner programs (i-to-i.com)
Spend a week or more building homes for the underprivileged in Costa Rica, living with a local family.

For voluntourism operators who specialize in specific countries or regions, go to cntraveler.com/makeadifference.