Here's a few more I copied from a "Google" search:
Dirr, M.A. 1997. Michael Dirr's Photo-Library of Woody Landscape Plants. PLANTAMERICATM. Locust Valley, NY (1-800-PLANTCD). $149.95. CD
Flint, H.L. 1997. Landscape Plants for Eastern North America, 2nd ed.. Wiley- Interscience, New York. On reserve in Lilly Hall of Life Science Library.
Gilman, E.F. 1998. Horticopia. Trees, Shrubs, and Groundcovers, 2nd Ed. Horticopia, Inc. Purcellville, VA. $150.00. CD
Gilman, E.F., et al. 1996. Southern Trees, 2nd Ed. University of Florida and USDA Forest Service, Southern Region. $129.95. CD