Was out there recently...
Golden Earthworm Farm, Jamesport
I don't know why but their yellow cherry tomatoes are incredible. Also the best garlic I have every cooked with. Worth driving out just for the tomatoes and garlic (other stuff is also awesome especially the beets), but, they are also at Islip, Huntington and Port Washington Farmer's Markets. Get to the farmer's market early because they sell out of stuff quickly. One bonus at the the farm, the day I was there they were selling homemade chocolate chip cookies.
The Village Cheese Shop, Mattituck
Great cheese shop with great staff. 8 year aged Canandian Chedder is a standout, but other great cheese. They also have sandwiches. Kept hearing great things about Love Lane kitchen across the street, but I have not tried.
Wood Side Orchards, Aquebogue
New place making cider. They have four varieties, $8 for a tasting includes a pint glass you take home. No bottles yet, but you can buy a growler. I liked the traditional style which was not as sweet and the apple-raspberry.
Greenport Harbor Brewery Tap Room, Greenport
Great beers and a great tasting room. As with the cider comes with a glass you can take home. For commuters, I was stoked to see a couple of days ago that the beer tap line in Rosa's Pizza had Greenport's Harbor Ale on tap.
Pies are bit different in style than Briermiere, more buttery of a crust, works well with cherry pie. In the past I've gotten great tomatoes there, but this year's batch seemed a little flat. Of course, still infinitely better than supermarket ones and overall still a good tomato. They have great asparagus in the spring. Peaches are good here as are the apple cider donuts.
Snowflake Ice Cream
It's getting to be that I can't come near Riverhead without stopping here for an ice cream. Great down to earth ice cream. They use local stuff when possible without getting religious about it. Great flavors of the week (https://www.facebook.com/pages/Snowfl...).