I really enjoy my experience at Stiver Mill Farmers' Market.
Happens every Sundays from end of June to Mid October and held in the newly rebuilt, restored and renovated to it's original, Stiver Mill in Main Street Unionville.
Though is smallish compares to others, most vendors here are from the area and really friendly!
If you go around 3:30 pm, a lot of the vendors even offers end of day sale!
And of course, after shopping there is the business area on Main St and Toogood Pond where you can enjoy the rest of the afternoon!