One of my favorite perennials, the Stinking - or Bear's claw - hellebore (Helleborus foetidus) is coming into its own as the night temperatures drop into the 20's. Plant it where you can easily see it from inside the house, and watch as it comes into all green bloom in winter. It may appear to suffer in extremely cold, harsh spells, but will amazingly resurrect itself on warm days.
I put this one just outside the sliding doors to the terrace. It will get morning light on bright days, plenty of water from the drip line of the roof, and good drainage since it's planted in gravel. If past experience with this plant proves true, it will self seed, forming a colony in a year or two.
And it does not stink at all.