I've written about volunteering in Peru before. There are tons and tons of organisations out there. This organisation was started by Jim Killon, who is from Baltimore, Maryland. In 2009 he fulfilled a long-time dream of developing a project for the benefit of children living in a 3rd world country. He is an exhibited artist and photographer, writer/author and a social activist. He wrote an article about how volunteers have helped out. You can read the article at Volunteer Match.
His “Haz lo Correcto – Do the Right Thing” campaign in Huaraz, Peru has increased community awareness toward positive development there. He just wrote ae e-book, “A Gringo in Peru – A Story of Compassion in Action,” and it has already reached readers in seven countries. You can find it on Amazon or Lulu.