Here are some other useful websites for similar services based off a time honored tradition known as 'gleaning' which has been used since ancient times to feed those without the means to purchase food:

http://gleanings.org/
http://www.villageharvest.org/harvestingdirectory

Most are organizations based in California, but I'm sure if you contacted them they'd put you in direction for your local gleaning/volunteering organization.

A cool Ag-tech app is called crop-mobster which, while not always free, is still a cool service worth a mention (they sell excess produce to the public on the farm at a discount).

http://cropmobster.com/