All About Optics: Advice about selecting optics for birding and reviews of binoculars and spotting scopes. Sponsored by Eagle Optics.
Audubon Society Guide to Binoculars: Guide to buying binoculars from the National Audubon Society.
Better View Desired: Birding optics reviews, articles, manufacturers, and retailers.
Bird Watcher's Digest: OpticsFinder: Collection of articles from the magazine on all aspects of buying binoculars and spotting scopes.
Birding Optics: Binoculars and Scopes: Articles by Michael and Diane Porter on how to choose and use them, comparison charts of top brands, and how they work.
BirdScope: Information about birding with Tele Vue telescopes, with telescope and accessory selection guides, specifications, reviews, usage notes, and dealer list.
Eagle Optics: Resource for Binoculars and Spotting Scopes for Birding, Hunting, Nature, Sports, and Outdoor Recreation. See Complete Online Binocular Catalog and Buying Guide.
Mike's Birding Blog: Reviews of optical equipment for birding and digiscoping. Articles and pictures about birding.
Optics4birding: Sells binoculars, scopes, and tripods. Includes reviews, articles on optics basics and a buying guide.
WorldTwitch - Binoculars and Spotting Scopes for Birding: Comparison of popular binoculars and telescopes used by birders, with recommendations.