General advice for finding volunteer work is to ask at language schools; they usually know of several programs suitable for their students. Both nonprofit and for-profit organizations can arrange volunteer opportunities, if you contact them in advance.
Action Without Borders (www.idealist.org) Online database of social work–oriented jobs, internships and volunteer opportunities.
Cross-Cultural Solutions (www.crossculturalsolutions.org) Educational and social-service projects in Lima and Ayacucho; program fees include professional in-country support.
Earthwatch Institute (www.earthwatch.org) 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.
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.