BiologyBase

Checklists, articles, and links for the world of life.
http://www.biologybase.com/

Integrated Taxonomic Information System

Authoritative taxonomic information on plants, animals, fungi, and microbes of North America and the world.
http://www.itis.usda.gov/

World Biodiversity Database

A growing taxonomic database and information system that aims at documenting all presently known species (about 1.7 million). Taxonomic trees, descriptions, synonyms, literature citations, and molecular database queries.
http://www.eti.uva.nl/Database/

BioImages - Virtual Fieldguide for UK Biodiversity

Large selection of pictures of organisms, mostly British in origin. Images are an aid to identification, showing different stages, states and views of the organisms. Search the database or follow a taxonomic tree.
http://www.bioimages.org.uk/

Natural Perspective

Dedicated to the beauty and science of nature and to the joys nature brings to those who explore it. The material here is organized according to the biological principles of Taxonomy.
http://www.perspective.com/nature/index.html

Discover Life

Information about taxonomy, natural history, distribution, abundance, and ecology of many species worldwide. Includes tools to identify, map, and database species.
http://www.discoverlife.org/

ARKive

Non-profit initiative of The Wildscreen Trust with photographs, movie clips, sound recordings, and brief desriptions of selected endangered and protected species of Britain and the rest of the world.
http://www.arkive.org/

Natural Selection

A gateway to quality, evaluated Internet resources in the natural world co-ordinated by The Natural History Museum, London.
http://nature.ac.uk/

Kingdoms Project

Project to establish web-based databases of organisms and other natural sciences subjects. Includes information about some taxonomic groups.
http://www.il-st-acad-sci.org/kingdoms.html

Lepidoptera and Other Life Forms

Taxonomic tree of mammals, insects, birds, and plants. Includes common and scientific names, publication details, references, links, general range maps, and some images. Most complete for Lepidoptera.
http://www.funet.fi/pub/sci/bio/life/intro.html

NCBI Taxonomy

Searchable and browsable taxonomy tree of organisms for which there are publicly available gene sequences.
http://www.ncbi.nlm.nih.gov/Taxonomy/taxonomyhome.html/

Canadian Version of Integrated Taxonomic Information System

Searchable database of four kingdoms: plant, animal, fungi, monera. Search by scientific or common names, English or French.
http://sis.agr.gc.ca/pls/itisca/taxaget?p_ifx=aafc

Mikko's Phylogeny Archive

A compilation of various phylogenetic trees representing different views of taxonomy. Includes links to other taxonomic websites.
http://www.fmnh.helsinki.fi/users/haaramo/index.htm

BioLib

Taxonomic tree of plants and animals with a photo gallery and some checklists for the Czech Republic and Slovakia. In Czech and English.
http://www.biolib.cz/

Biodiversity Explorer

Classification of all forms of life, with some photos. Has a strong South African emphasis.
http://www.museums.org.za/bio

BIOSIS Resources

Includes the Index to Organism Names, a publicly available subset of TRITON the Taxonomy Resource, and the Zoological Record Thesaurus.
http://www.biosis.org.uk/free_resources/

Flora and Fauna of the Great Lakes

Provides access to materials from the fish, mammal, and fungus collections of the University of Michigan, USA. Includes many images of specimens.
http://www.lib.umich.edu/programs/greatlakes/

Survey of the Plant Kingdoms

Explores plant anatomy, taxonomy, and classification, from Monera through the higher plants. Includes descriptions as well as graphics and schematics.
http://home.manhattan.edu/~frances.cardillo/plants/intro/

Census of Marine Life

A global network of researchers engaged in a ten-year initiative to assess and explain the past, present, and future diversity, distribution, and abundance of marine life in the oceans.
http://www.coml.org/

World's Boreal Forests: Animal and Plant Species

Fact sheets and photos for mammals, birds, trees and other plants of boreal regions.
http://www.borealforest.org/world/world_species.htm

Canada's Aquatic Environments

Provides comprehensive information about the aquatic habitats, animals, and plants of this country.
http://www.aquatic.uoguelph.ca/

HabitasOnline

Information on the plants, animals, and fossils of Ireland. Includes an encyclopedia of marine life of the UK. From the Ulster Museum Sciences Division.
http://www.habitas.org.uk/

Utah Conservation Data Center

Database of photos and fact sheets for animals and plants occurring in this state. Includes lists of sensitive, threatened, and endangered species.
http://dwrcdc.nr.utah.gov/ucdc/

Nature of New England

Photos, facts, and links to information about birds, butterflies, mammals, and wildflowers of this region.
http://www.nenature.com/

Wikispecies

Wikimedia Foundation project that aims to catalog all species.
http://species.wikipedia.org/

Tree of Life

Phylogenetic tree with information about the diversity of organisms on Earth, their history, and characteristics. An on-going multi-authored project hosted by the University of Arizona.
http://tolweb.org/tree/