Recommended reading and sources for descriptions:
          Batdorf, Lynn R., Boxwood Handbook  published by the  
                       American Boxwood Society, P.O. Box 85
                                       Boyce, VA 22620
          Dirr, Michael A., Manual of Woody Landscape Plants,
                              Stipes Publishing Company,
                              10-12 Chester Street,
                          Champaign, Ilinois 61820

Buxus sempervirens 'suffruticosa' -- English Boxwood.  Classic shrub  used in formal gardens, slow growing,  but can attain heights  of six to ten  feet if one is patient enough. 

Buxus sempervirens 'Vardar Valley'.  Originally from Macedonia, this plant has dark green foliage, and a mounded growth habit. 

Buxus sempervirens 'Elegantissma' -- Variegated Boxwood.  This pretty  plant has a creamy white margin around the edge of the leaf whose center is green.  Somewhat slow growing but will   reach a height of 2 feet in 10-15 years or so.

Buxus microphylla var. insularis 'Tide Hill'--also known as Buxus sinica var. insularis 'Tide Hill'--this has rather open graceful foliage,   a  spreading habit and will grow to about 2 feet high and 4 feet  wide.