Have you been hearing about the economic and environmental benefits of buying local produce, but are unsure of how to go about looking for the resources necessary to find what you need? Look no further! LocalHarvest.org, founded in 1998, is a very helpful website that shows you farmers' markets, grocery stores, and many other places where you can get sustainably-grown produce, grass-fed meats, and lots of other interesting goods.
Here's a screenshot of the map on the front page zoomed in on Ann Arbor.
And there's no reason to think that produce will be unavailable during the winter months, either-- some of these places offer frozen or preserved foods as well as fresh.