Botany Encyclopedia - Includes a botanical dictionary, advice for gardeners, and a store selling plants.
Botresearch USA - a botanical research and biotechnology organization specializing in tissue culture, photomicroscopy, and the production of educational materials for universities.
Center for Plant Conservation - Collaborative organization dedicated to conserving and restoring the rare native plants of the United States. Includes information on conservation techniques.
Cladistics or Supercilious? - Textual review of the development of evolutionary trees in botany. Written by Henry Loconte.
Glossary of Botanical Terms - Contains more than 2,500 terms relating to botany, gardening, horticulture and landscape architecture. Fully searchable and it is regularly updated.
Institute for Plant Ecology - Information about research and teaching activities with focus on biodiversity and ecophysiology in different climatic regions, based at the University Münster.
Max Planck Institute for Plant Breeding Research - Conducts research programs on molecular-biological, genetical, biochemical, physiological and cytological aspects of plant development and plant breeding. [English and German versions available.]