Fraser Fir (Abies fraseri) is perhaps the most popular. 

This stately fir was named for John Fraser, a Scottish botanist who explored the southern Appalachian Mountains in the late 18th century.  This species is closely related to the Balsam fir (Abies balsamea), which grows farther north. The Fraser fir grows naturally at high elevations in southwest Virginia, eastern Tennessee and western North Carolina.  The Fraser fir is known for its uniform, compact, pyramid shape and sturdy branches.  The needles are short and, interestingly, dark green on the upper surface and light, blue-green on the bottom surface.  The Fraser fir has a refreshing fragrance and retains its needles well.

Douglas fir (Pseudotsuga menziessii)

Was named after another Scottish botanist, David Douglas, who began cultivating the tree in 1826.  The Douglas is not a true fir, meaning it is not a member of the genus Abies.  Rather, its distinctive cones landed it in the genus Pseudotsuga, meaning false Tsuga.  The Douglas fir is indigenous to central California, western Oregon, Washington, and parts of Alaska.  It is characterized by its pyramidal shape with medium to dark green needles.  Like the Fraser, the Douglas fir is cherished for its lovely scent.

White Pine (Pinus strobus)

Many, however,  prefer the White Pine (Pinus strobus) as their Christmas tree. The Eastern White Pine is native to eastern North America from Minnesota to Georgia.  The White Pine was harvested by loggers in colonial times as its wood was used for masts, floors, and furniture.   It is characterized by its bundles of long, blue-green needles and slender cones.  Several dwarf cultivars are used in landscaping for screening and ornamental plantings