Worldwide Workers on Organic Farms (WWOOF) is a global organization started in England, WWOOF (originally Weekend Workers on Organic Farms) is a collection of farms and members across the globe. By becoming a member of WWOF, you join the network, and can work on organic farms across the country (and around the world) in exchange for a place to sleep, and food to eat.
Membership is about 25$ a year, and most places expect about 5-6 hours of work in exchange for 3 meals, and a bed at night.
USA Website - directory is pasword protected
Formerly listed under WWOF