General advice for finding volunteer work is to ask at language schools; they usually know of several programs suitable for their students. South American Explorers (SAE) has an online volunteer database and also folders with reports left by foreign volunteers at the SAE clubhouses in Lima and Cuzco.
Both nonprofit and for-profit organizations can arrange volunteer opportunities, if you contact them in advance.
Action Without Borders Online database of social work–oriented jobs, internships and volunteer opportunities.
Cross-Cultural Solutions Educational and social-service projects in Lima and Ayacucho; program fees include professional in-country support.
Earthwatch Institute Pay to help scientists on archaeological, ecological and other real-life expeditions in the Amazon Basin and the Andes.
Global Crossroad Volunteer, internship and job programs in the Andes. Summer cultural immersion programs for 18- to 29-year-olds include language instruction, homestays, volunteer work and sightseeing.
Global Volunteers (www.globalvolunteers.org) Offers short-term volunteer opportunities helping orphans in Lima.
HoPe Foundation Provides educational and healthcare support in the Andes.
Kiya Survivors/Peru Positive Action Organizes two- to six-month volunteer placements for assistant teachers and therapists to work with special-needs children in Cuzco, Urubamba in the Sacred Valley and Máncora on the north coast.
Volunteers for Peace Places volunteers in short-term work-camp programs, usually in Lima or Ayacucho. Program fees are more than reasonable and may be partially paid directly to local communities.