1) P.H.S.N.E. (Photographic Historical Society of New England).
2)The Daguerreian Society / Pittsburgh, PA
3) Metropolitan Post Card Club of New York City. A terrific historical resource of the artists, photographer's, publisher's, etc. of post cards.
4) Cycleback.com. A guide to judging the authenticity of photographs.
5) Luminous Lint. For collector's and connoisseur's of fine photography.
6) Stereoviews.com. THE website for stereoviews, and much more.
7) "Nineteenth Century Photographic Cases and Wall Frames" by Paul K. Berg. Second Edition, 2003. Available for purchase at his website, Berg's book is a remarkably thorough and scholarly work, and is an essential reference source for any collector or dealer of 19th century vintage photographica.
8) Photo Central.
9) Dennis A. Waters Fine Daguerreotypes. Simply the best.
10) Jeffrey Kraus Antique Photographica.
11) Christopher Wahren Fine Photographs.
12) KaufmaNelson Vintage Photographs.
13) Stereographica.com. Antique Photographica.
14) Greg French Early Photography.
15) Steven Evans Vintage Photography.
16) Half Pond Antiques. Specializing in vintage and antique photography.
17) Paul Frecker London-Nineteenth Century Photography. An online gallery selling various formats of antique photography.
18) The Library of Nineteenth Century Photography.
19) Jan Lagendijk's Stereoview Heaven. Fine stereoviews from 1860 to the early 1900's.
20) Pierre Spake Photography. Photography, Works on Paper, Works of Art.
21) MyDags.com. Dan Hadley Proprietor.
22) Vernacular Photography- Great images by as-yet unappreciated and undervalued artists.
23) Andreas Wiemer-American Presidential Autographs.
24) Lanterna Magica / Libreria-Galleria-Edizioni.
25) AmeriCollector.com. Events, news and information for collectors.
26) Playle's Online Auctions. As well as a link to multiple dealers of post cards, ephemera, etc., this site contains an excellent reference guide to the dating of real photo post cards.
27) Biblio.com An excellent online source for collectible books, many of them photography.