If your state salts the roads in the winter, it's strongly recommended to undercoat your vehicle with a coating to preserve it from rusting and shortening its useful life. Fluid Film is one of the better coatings, and is based on sheep lanolin, so it's not toxic to the environment.
4wheel drive is nice, but tires are EVERYTHING. You absolutely cannot rely on all season tires, you MUST get proper Winter tires if your region snows heavily, or you will have a bad time.
There are now fabric snow 'socks' for cars that act like snow chains to get you out if a bind, which would be worth having in the trunk.
In the winter, ALWAYS bring winter rated clothing in the car along with water, a small amount of food, heavy duty blanket, and a small liquid paraffin candle for heat in the event you get stuck in a storm, or go off the road from ice.
I looked into them a while ago, and from what I can find, they seem to be legit in that they really do use the profits for tree planting.