Natural Perspective: The Protoctist Kingdom (Protoctista) - Describes the kingdom as "a catch-all for the multicellular organisms which don't fit into the Animal, Plant, or Fungus Kingdoms" and describes its scope.

The Euglenoid Project - A comprehensive database of the taxonomy, structure, evolution, and general biology of the euglenoid flagellates, including the genus euglena.

Freakin Fucus - Introduction and technical information regarding seaweeds and related plants.

Seaweed Site - Algae-L discussion list, book list, comprehensive information, and photographs.

The Center for Phycological Documentation - Information about algae and their taxonomy, including 'The Catalogue of the Benthic Marine Algae of the Indian Ocean,' and 'The Index Nominum Algarum,' a compendium of circa 200,000 algal names.

Protozoa - Taxonomy and public-health information for the phylum.

Introduction to the Chromista: From Microbes to Giants - General discussion of the kingdom-level taxon Chromista, including diatoms, kelp, downy mildew, and other organisms that possess chlorophyll and are mostly photosynthetic, but are not plants. Includes links for more information.

Photos of Algae - Images of about 20 genera from the El Eden Ecological Reserve, Mexico.

World of Algae - Basic information and links to resources about algae.

Caribbean Reef Plants - Sample pages and images from an identification guide to marine algae and seagrasses.

Algae of the Keweenaw - Large image gallery of freshwater algae from the Keweenaw Peninsula, Michigan.