Farm Stands and the Honor Box — a stop on Vermont Route 100.
You'll pass roadside stands all the way down this road, and I'd encourage you to actually stop at one, because they're one of the genuinely distinctive things about driving in Vermont.
Many of them are unstaffed. There's a table, a hand-lettered sign, and a coffee can or a slot in a wooden box. You take what you want and you leave the money. Nobody is watching. That system has been running in this state for a very long time and it mostly works, which tells you something about the place.
What you'll find depends on the month. Spring: maple syrup, and if you're lucky, fiddleheads — the curled young shoots of ostrich fern, which are a genuine local delicacy and taste like a cross between asparagus and spinach. Summer: sweet corn, berries, flowers, eggs. Autumn: apples, cider, squash, pumpkins, and syrup again.
On syrup, one practical tip: buy it here rather than at the airport, bring cash, and don't be afraid of the dark grades. Golden is delicate and expensive; Dark Robust is what most Vermonters actually put on their pancakes and it has far more maple flavor.
Small bills are appreciated. Nobody at an honor stand can make change for a fifty.