Strawberries (Fragaria ananassa) - Perennial hardy to zone 2. Features pretty white flowers in spring. Edible fruits. Can be planted in a garden bed or grown in containers.
Info about using strawberries as edible landscaping:
http://www.garden.org/ediblelandscaping/?page=edible-strawberry...
I'm in zone 4 in Wisconsin, not quite the same climate as Maine, but it's cold here. I started my peanuts in the greenhouse last weekend. We ordered jumbo virginia peanuts from Gurney's. Gurney's says they need 4 frost free months to mature, and they are supposed to be good for up to zone 3...