Public Gardens

Chanticleer
Longwood Gardens
Morris Arboretum - of the University of Pennsylvania. Official arboretum of the Commonwealth of PA.
Scott Arboretum - of Swarthmore College
Temple University
Tyler Arboretum

Plant Selection and Care

Oregon State University - Landscape plant photos and information.
University of Delaware Botanical Garden
Ohio State University - PlantFacts
Penn State University Cooperative Extension - Horticulture/Gardening Page
University of Connecticut Plant Finder
Pennsylvania Horticultural Society Gold Medal Plants
United States National Arboretum - see their introductions. Great site for Crape Myrtles.
University of Rhode Island Greenshare Factsheets - Answers to gardening questions.
See their Sustainable Trees and Shrubs List.

Insects and Diseases

Ohio State University Cooperative Extension
PSU - Woody Ornamental Insect, Mite, and Disease Management