Wwoofing is an acronym for World Wide Opportunities on Organic Farms. It is a work-exchange program, and in exchange for labor, a "wwoofer" receives food, accommodation, and an opporunity to learn about organic farming.
Various organizations link wwoofers and farmers together - the beauty of the system being that, a farmer can offer a critique about a wwoofer, and the wwoofer can offer a critique about a farmer.
Finding a good wwoofer, and even finding a good farmer can, at times, be challenging, and there are many considerations for both the wwooffer and the farmer. "Look before you leap" may be apropos for both parties when delving in to wwoofing.
Here are some links to various wwoofing websites: