Find an empty spot of garden. The vegetable garden is perfect for this. It's looking sparse by mid-fall. Dig a trench or pit and cluster all your unplanted, potted plants together. Fill in the trench and the plants will think they're in the ground. The roots will be protected, but being in pots, they'll be that much easier to dig in the spring. They'll also be that much more ahead of the game when you do go to plant them, because keeping them in pots means the roots will not have been disturbed by lifting the plant out of the soil.
This method will also work with perennials that you've been growing in containers, but don't want to bring inside. Keep in mind that many decorative containers, like terra cotta and some plastics, will crack if exposed to freezing temperatures.
If you're not up to that much digging, you can get almost the same protection in Zones 6 and 7, by clustering the pots and insulating them with mulch or compost.
