For Your Cat
Consider treating your feline to a cat cave made of wool. It's a good insulator and kitties love to rest inside it. For cheerful ones, check out Dharma Dog Karma Cat.
For Your Dog
Pick up a memory foam bed. It's particularly great for older dogs since the cold can make their joints stiffer and achier. Foam mattresses tend to be warmer than other types, and it helps to be warmer year-round. Some great brands are the Brindle beds and the Orvis memory foam bolster beds. Keep a faux-fur throw on the end of your bed, if that's your pup's preferred sleeping spot, to keep him warm. Just remember, since your pup has a fur coat, placing a bed near a radiator or heating vent may be too warm for him causing him to avoid his bed if placed in such an extra warm spot.