General

• United States Department of Agriculture, Plants Database
• Flora of North America Project
• Illinois Plant Information Network
• Illinois' Best Plants, Chicago Botanic Garden
• The International Plant Names Index

Threatened and Endangered Plants:

• Center for Plant Conservation, National Collection of Endangered Plants
• Illinois Department of Natural Resources, The Illinois Endangered Species Protection Board
• Indiana Department of Natural Resources, Endangered Species
  1. List of Endangered, Threatened and Rare Species by county (list of PDF files)
  2. Endangered, Threatened, and Rare Vascular Plants of Indiana (PDF)
• Wisconsin Department of Natural Resources, Wisconsin State Threatened and Endangered Species

On-line guides:

• UW-Stevens Point -- Plants of Wisconsin
• UW-Green Bay -- Pteridophytes of Wisconsin: Ferns and Fern Allies
• Missouri Plants - Photographs and descriptions
• Discover Life's IDNature Guides
• Plant Systematics.org's on-line key to Dicot Families - Click on Diagnostic Keys, then choose Key to Families of Dicotyledons

Online plant glossaries:

• GardenWeb Glossary
• California Plant - Botanical Terms

Information on plants for cultivation or other uses:

• Chicago Botanic Garden - Plant Information
• Chicago Botanic Garden - Illinois' Best Plants
• Chicago Wilderness - Landscaping with Native Plants
• New York Botanical Garden - Home Gardening Online (requires Free Online Subscription)

Poison Control Center 800-222-1222

Illinois

• Naturalist Certificate Program
• The Morton Arboretum
• The Field Museum
• Chicago Botanic Garden

Indiana

• Indiana Master Naturalist Program