My favorite is an offering of Shipyard (of Portland, Maine), their Longfellow Winter Ale. Though cursed with a lavender label bearing the homely mug of Portland's favorite son, it's a delicious, rich black Winter ale. I haven't seen it on offer for a while, so maybe it's been replaced by their strong Prelude Winter Ale, also a cold-weather fave.
Catamount, the recently defunct Vermont brewery, used to brew a fantastic Christmas Ale. I used to buy a case of it every winter. On one leaf-peeping tour through White River Junction years ago, I stopped at the brewery and the only person there was the guy who was transferring their just-fermented Xmas brew to the conditioning tanks. He gave me a preview taste of the unfiltered, uncarbonated product.
Portland, Maine's other great brewery, D.L. Geary's, makes a rich Hampshire Special Ale which used to be "only available while the weather sucks." Now it's available year-round. No guarantees on the weather.
regards,
Esteban Hambre