WARNING: Strictly speaking, if you are a foreigner it is illegal for you to volunteer in Indonesia. You should check with a listed organization to check on your status if you are accepted as a volunteer with them. The following link provides detailed information on this issue.

http://indonesiaexpat.biz/other/volunteering-in-indonesia/

Bali

Java

Sumatra

Sulawesi

Kalimantan

Aceh