These are the references I've used to identify the plants in these pictures.  For common names and scientific nomenclature, I've used the books specific to New Jersey or Indiana for their respective photos.  The web sites listed below have also been useful in cross-checking plant identification.

Books

Wildflowers in the Field and Forest: A Field Guide to the Northeastern United States, Steven Clemants and Carol Gracie
Wild Orchids of the Northeast: New England, New York, Pennsylvania, and New Jersey, Paul Martin Brown
Field Guide to Indiana Wildflowers, Kay Yatskievych
Orchids of Indiana, Michael A. Homoya

Websites

USDA PLANTS Database
Plants of the NJ Pine Barrens
Plants of Southern New Jersey
Connecticut Botanical Society
NY - NJ - CT Botany Online
Missouri Wildflower Guide