Boxwood (Buxus microphylla): Although boxwood is generally not considered hardy past zone 4, it will probably survive in a sheltered location, especially if it has adequate snow cover. Korean boxwood, at 2 1/2 feet tall and wide, is the hardiest variety, but 'Winter Beauty' is also quite hardy, and will grow to 3 feet tall and up to 4 feet wide. The leaves remain green throughout the winter, and because it grows very densely it is ideal for a small hedge or to create topiary forms.
Dwarf European Cranberry (Viburnum opulus 'Nanum'): This relative of the American Highbush Cranberry grows only 2-3 feet tall and 3-5 feet wide. It is a very tidy, compact shrub that is very shade tolerant, but unfortunately it, unlike its larger relatives, has little or no flowers, fruit or fall colour.
'Tilden Parks' Ninebark (Physocarpus opulifolius 'Tilden Parks'): Although most ninebark varieties require at least half a day of sun, the variety 'Tilden Parks' will tolerate quite dense shade, as well as sun. It also grows less than two feet tall, with a spread of up to four feet, making it a good groundcover with dense green foliage. It doesn't flower, but it does a good job of suppressing weeds.
Snowball (Viburnum opulus 'Roseum'): Although a snowball bush prefers partial or full sun and moist soil, it is surprisingly adaptable to poorer conditions. It blooms with large, white, hydrangea-like flower clusters in late spring, and it grows up to 10 feet tall and wide. It can also be trained to grow as a small tree. Although its flowers are spectacular, it produces no berries, making it a good choice near a deck or walkway.
Snowberry (Symphoricarpos albus): This undemanding plant grows 3-4 feet tall and wide, with small, pinkish-white flowers in mid-summer, followed by striking, white berries. The berries are not edible and aren't even said to attract birds, so they provide ornamental value through the winter, if you can see them against the snow. This bush tends to sucker, which can be a benefit if you want it to fill in an area or to grow it as a hedge, otherwise, the suckers can be controlled by pruning. Although it is generally a tidy-looking bush, pruning to thin the branches can help it resist the disease powdery mildew.
Sumac (Rhus aromatica, Rhus glabra, Rhus typhina): There are many different varieties of sumac, the largest of which can grow up to 23 feet tall and can be trained to grow as a tree. Cut-leaf and Staghorn sumac both have lacy-looking, divided leaves that give it an almost tropical appearance. Fragrant sumac is much smaller; 'Gro-low' is the most shade tolerant variety and grows only 2 feet tall. It has fragrant yellow flowers in the spring and red fall colour. Although it is a good groundcover, you may find that it eventually spreads beyond its allotted space. All sumacs sucker and can be used to fill in an area, or they can be planted in a confined area where they won't spread out of bounds.