Broad leaved evergreens, Rhapidophyllum hystrix, Sabal minor, dwarf conifers, japanese maples(bark and structure), Stewartias, and Franklinia(4 season interest).

My winterberry holly is FANTASTIC right now. Bright red berries covering the bare branches. They really look good against a backdrop of snow (which the "warm" weather and rain has currently washed away, of which I am NOT complaining!!). Evergreen hollies (such as our native Ilex opaca) also look good.

I have Skimmia japonica female - red berries that often last till spring , Skimmia japonica 'Rubella'- great red big buds from fall till spring and Rohdea japonica -looks like evergreen Hosta.
Ivy

If you look up Eastern Plant Specialties and check winter color there is alot of information available. I've never used this mail order nursery. It seems they just moved to Clark N.J. GardenWatch gives mixed reviews.
Rosa Virginiana has glossy red canes and twigs and small red red fruit all winter. It needs full sun and it suckers so you have to plant it in a larger space ( 5ft ) . Treat it like winterberry holly and cut old canes because it's the newer canes that have the red color. It has the added advantage of fragrant flowers in June.
I don"t know if it's still available but "The Four Season Landscape" by Susan Roth , Rodale Press 1994, is an excellent
book.
Pixie

Stay away from Eastern Plant Specialties, Pixie. That's all I'm going to say on that subject.

The current edition of Gardener's News, Sugar Magnolia, has a couple of articles with recommendations for interest in the winter garden. It's a freebie that you might be able to find at a local garden center.

In the same edition, there's a tribute to a wonderful person, Ron Enyingi, with whom my son got his start. Every word of the article is true.

Thanks for the nursery info NJTea on Eastern PLant Specialties . Any input on Edge of the Woods Native PLant Nursery?
Would it be better to start a new thread on mail order nurseries? Sorry Sugar Magnolia if I'm infringing on your posting.
Pixie

Winter is a great time to visit arboretums and botanical gardens. They are very good at scoping out winter interest plants beyond conifers. You will definitely find some wonderful things. This is more or less how I break it down for myself.
1.Conifers - personally I try to find conifers beyond junipers and arborvitea (though I never exclude any group). There are a lot of different colors, textures here. Check out from the library Conifers: The Illustrated Encyclopedia (2 Volumes) by D. M. Van Gelderen and J.R.P. Van Hoey Smith - unless you want to buy them. Also Gardening with Conifers by Adrian Bloom and Richard Bloom.
2. Broadleaf evergreens, trees, shrubs, subshrubs. These come with flowers and are often scented, a favorite group of mine.
Magnolia Grandiflora - very shiny winter leaf with indumentum - fuzzy brown felt underneath.
Kalmia
camellias
Rhodies and azalea
pieris
skimmia
Sarcococca
boxwoods
Evergreen ilex - several types, some variegated
leucothoe
euonymus - lots of choices here
Osmanthus Goshiki
...to name a few

3. Trees with beautiful bark: Besides the beautiful gray plates of your typical mature tree, there are other textures and colors to choice from. Go check out the tree gallery now for some tree bark shots.
Acer griseum
Stewartia pseudocamellia
coral bark maple
coral bark willow
prunus serrula
river birch and other birches
Seven Sons Tree
crape myrtle
pinus densiflora
cryptomeria
many others

4. twig color, texture: Many shrubs are not evergreen but are still colorful in winter. Look into salix and cornus for a lot of examples. Also
Kerria japonica
roses
oakleaf hydrangea
ninebark
spireas
Sand cherries and some deciduous ilex have very black bark
Saint Johns Wort

5. Persistant berries or colorful buds, cones: Some are more persistant than others.
skimmia as mentioned
pieris
ilex
viburnum
callicarpa
Crataegus - Hawthorn trees
Mountain Ash
roses for hips - many shapes and sizes, reds, oranges, greens, yellows
Magnolias -pussywillow like buds

6.shape: Some plants have better bones than others.
deciduous azalea
Harry Lauder's Walking stick
things called curly or contorta
Japanese maples weeping or not
Other weeping things like cherry and katsura

7. Perennials, groundcovers that don't die all the way back like:
heuchera
hellebore
sage
lavender

8. Perennial seedheads like
allium tuberosa (reseeds though)
stonecrop
astilbe

9. Finally, I look for plants that bloom early or very late to extend the season. I usually have flowers into December, sometimes January and starting up again in March or April, depending on the year.
witchhazels
winter jasmine
bulbs labeled late winter, early spring bloomers
hellebore - especially hellebore foetidus for me
pulmonaria
arabis

Ornamental grasses. Miscanthus sinensis looks good near rudbeckia and sedum seedheads. Japanese anemone have fluffy seedheads that are light up silver when the sun is behind them but they don't last all winter.

Wintersweet will start opening buds on warm days in Jan. but you have to bring it into the house to really smell it. Small waxy flowers in an odd chartreuse and burgundy combo.

Tree silhouettes, almost any.

Hollies of all types are one of my favorite winter plants.
Here is Ilex pedunculosa.

Wow, great suggestions everyone! Thank you. Maybe next year I will actually have a winter garden rather than skeletons from my Spring/Summer garden :-)

I was in Ringwood at the public library for a concert the other day. They have an outdoor reading garden (isn't that a nice thing?) and I could see they had evergreens in pots with some kind of plant with red berries (maybe the aforementioned holly?). I'm wondering how evergreens/perennials fare in pots over more than one season? Do you repot with fresh soil every year? Just fertilize? Hmmm.....

We had a potted topiary on our patio in a pretty sturdy clay pot. In the winter, something happened -- perhaps the moisture in the root ball froze -- and the pot split. We had to throw it out.

Clay doesn't overwinter well. The moisture inside the pot freezes, expands and breaks the pot.