WePatch allows members to find and list, by location, unused plots of land that are in need of a little gardening attention. Likewise, gardeners who do not have their own land are able to list themselves as gardeners in need of land. Once the two parties have found each other, an agreement can be made that will be mutually beneficial. Arrangements can be as simple as a handshake or a written agreement with complex clauses.
So, if you have a patch of land on your property being under utilized, why not let others know about it and put it to good use. Your garden could be growing vegetables and helping others to fulfil their gardening ambitions. This is mainly US based, but could be used elsewhere.