Cacti and Other Succulents
- Provides an overview of these drought tolerant plants and the convergent evolution which has resulted in there being similar looking plants from very different plant families.
- http://www.biology.ed.ac.uk/research/groups/jdeacon/desertecology/cacti.htm#top

Chihuahuan Desert Cacti
- Information and photographs of several species found in this region: Ariocarpus fissuratus, Epithelantha bokei, Echinocactus horizonthalonius, Ancistrocactus uncinatus, Echinocereus pectinatus and species of Echinocereus.
- http://www.biology.ed.ac.uk/research/groups/jdeacon/desertecology/chicacti.htm#top

Cactaceae
- Botanical characteristics of this family of plants with technical drawings of a number of species.
- http://delta-intkey.com/angio/www/cactacea.htm

Close-up View of Several Cacti
- Photographic study by Brian Johnston of these plants, with many fine images of flowers and spines, both macroscopic and microscopic.
- http://www.microscopy-uk.org.uk/mag/artjan07/bj-cacti.html

Cacti of Chile
- Photographs of several species including Austrocactus, Capiapoa, Echinopsis and Opuntia.
- http://www.chileflora.com/Florachilena/FloraEnglish/B_CACTUS_PLANTS.htm

Coryphantha
- Classification information, photo galleries, bibliography, distribution maps, and link directory. [German, English]
- http://mypage.bluewin.ch/retodicht/

Rhipsalis, Lepismium, Hatiora, Schlumbergera
- Information on plants in these four genera, including species lists with photos, cultivation and propagation details, and links to vendors and collections.
- http://www.rhipsalis.com/

Southwestern Cacti
- Information and photos for species native to the southwestern United States.
- http://www.whitethornhouse.com/cacti/cacti.htm

Keir's Botanical Photo Archive - Cactaceae
- Images from the US.
- http://www.keiriosity.com/cactaceae/cactaceae.html

Cacti Guide
- Images of many cactus genera as planted specimens in collections or in natural habitat, with horticultural advice and a discussion forum.
- http://cactiguide.com/

Peterocactus National Plant Collection
- List of the nine species, endemic to southwestern Argentina, with images and brief descriptions of four.
- http://www.manntaylor.com/ptero.html

Plants of the Cactaceae Family
- Large image gallery of cacti cultivated in Phoenix, Arizona.
- http://www.desert-tropicals.com/Plants/Cactaceae/

Mark Faint's Cactus Page
- Detailed information on Neolloydia, Notocactus, and Turbinicarpus.
- http://www.mfaint.demon.co.uk/cactus/

Outdoor Cacti Photos
- Photos of Opuntia, Echinocereus, and others, resources, and tips for growing and photographing them.
- http://www.xmission.com/~mbmiles/

Cactus Museum
- Photos and notes for many species from a cactus grower in Tucson, Arizona.
- http://www.cactusmuseum.com/

The Cactaceae
- Description of the cactus family, with photos and short profiles of several representative species.
- http://www.botany.hawaii.edu/faculty/carr/cact.htm