Can anyone recommend a good organisation to volunteer with in South America?

I spent three months in Peru with Volunteach Peru. It's a really good family run organisation who set you up teaching English in a school and living with a peruvian family whose children go to the school you're teaching in. You do have to pay for it but it's not nearly as expensive as a lot of other organisations and that includes your accommodation and food for three months! Peru is a fantastic country, so much to do and see, really cheap, the people are very friendly and the food is amazing! If you have any more questions feel free to email me! My email address is [email protected] . Hope this helps! 

Sounds fantastic, thank you so much :)

A couple of my friends volunteered with SKIP in Peru after they did a talk at our uni, working with kids in disadvantaged areas and it looks like they had a brilliant time.

I hope I'm not too late to answer, but I work for an organisation called Globalteer - we are registered UK charity and place volunteers in teaching assitant roles with an educational project for underprivileged children near Cusco. We also have fees but they do cover all your pre-travel information, in-country support (we have staff on the ground) accommodation, spanish classes, daily transport and so on. You can e-mail me at [email protected] or visit our website at www.globalteer.org. Good luck with your search!

International Citizen's Service  (ICS) http://www.volunteerics.org/ offer sustainable volunteering opportunities for under 25s all over the world. I went to a talk a few weeks ago about sustainable volunteering and being aware of your impact. There are a number of charities who working to raise awareness of the damagin effect of unsustainable lucrative volunteering tourism, ie, the opportunities you could pay thousands for, so watch out for these.