WWOOF
This organization, called Wwoof for short, operates worldwide with certain countries managing their own particular organization. The basic premise is a sort of international farmstay. In exchange for 4-5 hours of work per day, participants called, Wwoofers get room, board and the chance to meet some locals. The specific details are best found on the wwoof webpage, but in each country you pay a fee to get the host book which allows you to contact any hosts you like. Unfortunately, between the time I heard about wwoof and the time I actually got to participate, I'd kind of built it up to mythic status in my mind as the ideal travel organization, which it turned out not to be. That said, you can still have some pretty incredible experiences wwoofing.
The downsides of wwoof are that it is increasing in popularity as a cheap way to travel and work on your English if you aren't a native speaker. That means a couple things: first is that in popular areas, and in summer, it can be next to impossible to find any host that is able to take you. There were times when we called ten to twenty hosts and still came up empty. Second, it can be hard to convince hosts that you are actually interested in organic farming and are not just after a cheap place to crash for a while. Although the flipside of that is that many of the farms are really just big gardens and so if you are serious about organic farming, it can be difficult to find a host who takes it as seriously as you do.
Still, incorporating some wwoof visits into any travel is well worth the hassle arranging the visit might cause. We spent time on farms in some beautiful, out of the way places in New Zealand and Australia. They remain etched in our memories. Also, the people we stayed with during our wwoof visits, were among some of the most interesting we encountered.