In Honaunau-Napoopoo we are staying, in Hawaii, we found a great organization of WWOOF.
From their website:
WWOOF is a world wide network of organisations.
We link volunteers with organic farmers, and help people share more sustainable ways of living.
WWOOF is an exchange - In return for volunteer help, WWOOF hosts offer food, accommodation and opportunities to learn about organic lifestyles.
WWOOF organisations link people who want to volunteer on organic farms or smallholdings with people who are looking for volunteer help.