Algae Research, Royal Botanic Garden Edinburgh

ADIAC Diatom Image Database

Algaevision (UK Algal Image Database, Natural History Museum: images to accompany The Algal Flora of the British Isles: does not include diatoms)

British Phycological Society

Cyanosite (including image gallery)

Paul G. Davison, University of North Alabama

The Delwiche Lab, University of Maryland

Desmids.com (Michael Ells)

Protist Information Server

Phycological Society of America

Phytoplankton Key: An image-based key to algae, cyanobacteria and other aquatic objects (A.L.Baker)