Finding a farmer's market
For the US, try Local Harvest.  They list farms, farmer's markets, CSA, etc, and try to keep track of what sort of things are sold from each place (fruit, meat, etc.)

update : other places to ask around : the local farm extension office or your local farm bureau.  When I lived in Europe, it was easy -- they were large enough that everyone knew where they were, and it seemed that there was at least one per town, and there could be a dozen for larger cities.