Every Monday, Wednesday, Friday, and Saturday from 8am-6pm, The Council on the Environment’s “Greenmarket” operates a farmers market in Union Square featuring fresh produce and food stuff from local and New England farmers. The produce is great, the baked goods fabulous, and the meat and fish is as good as you will find in any NY restaurant.
Greenmarket operates the markets throughout the city and you can find one in some neighborhood every day of the week. Visit their website for a schedule.