Content Based Image Retrieval:
Surfimage
Content-Based Image Retrieval Systems: A Survey

Automatic Identification Systems:
Automatic Diatom Identification and Classification (ADIAC)
The Computer Vision Homepage
Dinoflagellate Categorisation by Artificial Neural Network (DiCANN)
Cyanobacteria Detection and Species Classification by Image Analysis

Algae general:
The Freshwater Biological Association
Phycological Society of America
International Phycological Society Web Site
British Phycological Society Web Site
The world of algae
The Algae Home Page / Dept. Botany, National Museum of Natural History, Smithsonian Institution
The virtual ocean
Microscopy UK Magazine
The Harmful Algae Page
Coded List of Freshwater Algae of the British Isles

Diatoms:
The Diatom Collection of the California Academy of Sciences
Diatom Home Page
International Society for Diatom Research
Schmidt's Diatom Atlas
European Diatom Database (EDDI)
South Florida Diatoms Databases
Australian Diatom Home Page
Mongolian Diatom Home Page
Klaus Kemp's diatom arrangements at Microlife Services
Skagerrak Phytoplankton
Diatcode and Amphora database (ECRC)

Desmids:
Desmids at Microscopy UK Magazine
Bill Ells' Desmid Pages
A recipe for desmid culture medium
Desmids of the Netherlands

Image databases:
Susquehanna University Algal Image Archive
Ohio University Algae Home Page
Protist Information Server Images Library
Florida University Diatom Images
Diatom Image Archive at University of Alberta
Bowling Green State University Image Archive
Eugene Stoermer's Great Lakes Diatom Home Page