You can contact a WWOOF network and against a small membership fee you receive a list of organic farms in your country of choice. You can then contact farmers directly and find a place to work.
Just before Christmas I went to a meeting of Greendrinks here in Brussels.
A group of individuals with NGO or corporate background that share a passion for environmental topics. Discussions about forestation, remaining fish stocks and how the recession impacts the environmental conscious behavior of corporates. At some point during the conversation you will find a common interest and exchange a website here and an email there… Networking the green way. I certainly enjoyed my Monday evening.
Greendrinks is a network that exists all around the world. Have a look at their site to see what’s going on in your city.
To give you a feel for the flavor of such an evening: Here a video from a Greendrinks event in Toronto.