Introduction to the Green Kingdom

Brief introduction to the plant kingdom with links to further information.
http://www.ucmp.berkeley.edu/plants/plantae.html

Names in Current Use for Extant Plant Genera

International Association for Plant Taxonomy searchable database.
http://www.bgbm.fu-berlin.de/iapt/ncu/genera/NCUGQuery.htm

Natural Perspective: Plant Kingdom

Introduction to the Plant Kingdom with information on some of the divisions which make up this group.
http://www.perspective.com/nature/plantae/

CalFlora Database

Searchable database all 8375 currently recognized vascular plants in California, including 20000 photographs.
http://www.calflora.org/

The Oldest Land Plants

Introduction to the first land plants, known from fossils.
http://www.xs4all.nl/~steurh/eng/old1.html

FloraBase - The Flora of Western Australia

Authoritative scientific information on 12,000 taxa in Western Australia, including maps, images, descriptions, specimen, and nomenclatural information. Requires registration.
http://florabase.calm.wa.gov.au/

International Plant Names Index

Database of the names and associated basic bibliographical details of all seed plants.
http://www.ipni.org/

Botanical Word Meanings and Name Derivations

References on California plant names, meanings and derivations from Latin and Greek roots, with biographical information on western botanists and collectors.
http://www.calflora.net/

Land Plants Online

Southern Illinois University's guide to the taxonomic and evolutionary relations among terrestrial plants, with extensive links to other resources.
http://www.science.siu.edu/landplants/

Forestry Images - Plants

Small collection of plant imagery, from University of Georgia.
http://www.forestryimages.org/plants.cfm

PLANTS National Database

Online USDA database of information, images, and links on plants in the USA, including crops and invasives. Search by name, geographic distribution, or other characteristics.
http://plants.usda.gov/

Index Nominum Genericorum

A collaborative project of the International Association for Plant Taxonomy and the Smithsonian Institution, providing a compilation of generic names published for all organisms covered by the International Code of Botanical Nomenclature.
http://rathbun.si.edu/botany/ing/

Dictionary of Botanical Epithets

Glossary of Latin terms used in species names, from abbreviatulus to yunnanensis.
http://www.winternet.com/~chuckg/dictionary.html

Synonymized Checklist of the Vascular Flora of the United States

Full text index of the 1998 version of the Biota of North America Program's checklist.
http://www.csdl.tamu.edu/FLORA/b98/check98.htm

Kingdom: Plantae

A growing directory of the hierarchy, from Kingdom down to species, with common names included, and descriptive pages on selected species.
http://www.cloudnet.com/~djeans/index.htm

Atlas of the Flora of New England

Continuing project with annotated checklists of pteridophytes, gymnosperms, and most monocots, with links to dot maps for each taxon.
http://neatlas.huh.harvard.edu/

Flora of Hokkaido

Distribution maps of vascular plants of Hokkaido, Japan.
http://www.hinoma.com/maps/index.shtml

Illustrated Flora of North Central Texas

Information including keys, descriptions and illustrations of species available in Adobe pdf format by Shinners and Mahler.
http://artemis.austincollege.edu/acad/bio/gdiggs/EastTX/ETinfo.htm

Hawaiian Native Plant Genera

Images of hundreds of species of ferns, fern allies, and flowering plants, arranged by genus.
http://www.botany.hawaii.edu/faculty/carr/natives.htm

Digital Flora of Texas - Vascular Plant Image Library

Large collection of photographs, arranged by family.
http://www.csdl.tamu.edu/FLORA/gallery.htm

Albion College Vascular Plant Image Gallery

Taxonomically arranged images and summaries of family characteristics.
http://www.albion.edu/plants/

National Herbarium Nederland

Information about the research themes and training undertaken at the national herbarium of the Netherlands, with links to the three contributary universities.
http://www.nationaalherbarium.nl/

University of Florida Herbarium (FLAS)

The herbarium and the associated paleobotanical collection have combined holdings of approximately 1/2 million specimens. Includes library search, catalog, and project information.
http://www.flmnh.ufl.edu/natsci/herbarium/

University of Manchester: British Flowering Plants

Searchable, illustrated collection.
http://emu.man.ac.uk/mmcustom/BotQuery.php

Glossary of Roots of Botanical Names

Meanings of over 1000 root words used in scientific names of plants.
http://garden-gate.prairienet.org/botrts.htm

Kew Record of Taxonomic Literature

Database of references to publications on the taxonomy of flowering plants, gymnosperms, and ferns.
http://www.rbgkew.org.uk/bibliographies/KR/

National Plant Data Center

Responsible for the PLANTS database, which focuses on the vascular and non-vascular plants of the United States and its territories, including checklists, species abstracts, distribution data, crop information, plants symbols and plant growth data.
http://npdc.usda.gov/

Plants For A Future

Information about a wide range of edible or otherwise useful plants, sorted by names and potential uses.
http://www.ibiblio.org/pfaf/

E-Flora BC

Electronic atlas project for the plants of British Columbia, covering life forms from vascular plants to algae, and topics from identification to scientific collections.
http://www.geog.ubc.ca/~brian/florae/