National Stereoscopic Association [https://stereoworld.org/]
Photographic Historical Society of New England [http://www.phsne.org/]
Magic Lantern Society of US and Canada [http://www.magiclanternsociety.org/]
View Lists by photographer, and Online Backissues of StereoWorld Magazine. Scroll down the entire page and click on the banners. Stereo Lists
The Stereoscopic Society (UK). This organization is primarily for contemporary photographers. Stereoscopic Society
The Stereoscopy Blog. Well researched and timely illustrated essays on all aspects of stereophotography balancing technical, contemporary and historic subjects.Includes event announcements. Thank you Rebecca!
The Classic is a free online magazine of historical photography. Download magazine pdfs or browse excellent essays in their Classic Platform
British Photographic History [http://britishphotohistory.ning.com/]
The Stereosite , run by Pascal Martine out of Mainz contains a mix of contemporary, how-to, and historic stereophotography subjects. He established a productive Virtual Stereoscopy Community which has a wonderful roster of recorded zoom-style lectures.
Keystone Mast Collection at U. California, Riverside [https://calisphere.org/collections/11747/]
New York Public Library Picture Collection Online [https://digitalcollections.nypl.org/]
US Library of Congress Prints and Photographs Online Catalog [http://www.loc.gov/pictures/]
Luminous Lint, an online collectors resource [https://www.luminous-lint.com/]
Getty Museum Digital Collections [https://www.getty.edu/research/tools/]
California Museum of Photography [https://ucrarts.ucr.edu/]
George Eastman House, Rochester, NY [https://www.eastman.org/]
Johnson-Shaw Stereographic Museum [http://www.johnsonshawmuseum.org/]
FBS Foundation for the study of the historical footprint of stereoscopic photography as science and art. A Spanish Foundation with image, hardare, and ephemera collections that will be displayed in a restored historic building. Founded by a pair of architect-designers (Yolanda Fernández -Barredo Sevilla & Juan José Sánchez García) they have multipronged goals of aggregating primary material, and leveraging its application in historical research and new digital projects. This is one to watch.
Stereo Photomaker software for digital presentation of stereoviews by Masuji Suto [http://stereo.jpn.org/eng/stphmkr/]
K&J Jacobson [http://www.jacobsonphoto.com/]
Jeff Kraus' Stereoviews. A US dealer in historic images of all formats. Stereos organized by subject.
World of Stereoviews . A UK dealer in original historic stereophotographs. Multiple formats (paper, glass). searchable.
London Stereoscopic Company Ltd. The LSC was revived by Brian May, and issues superb monographs at reasonable cost. Wide range of historical, contemporary (Brian May was a guitarist for Queen, and brought his camera!), and scientific (the multitalented Brian is also an astrophysicist) monographs. Some of the highest quality reproductions available.