WWOOF (Worldwide Opportunities on Organic Farms) is an organisation that promotes farm volunteering in places tha use organic methods.
Owners of farms can become hosts and get some help in their farms. People can become volunteers in any farm in many countries, and work there for a flexible period of time. It is an exchange, hosts offer food and accommodation, volunteers offer their help in the jobs needed. The only money involved is for becoming a member of the organisation so you can start participating.