Optics

Bird Watcher's Digest: OpticsFinder - Collection of articles from the magazine on all aspects of buying binoculars and spotting scopes.
http://www.birdwatchersdigest.com/optics/optics_index.html

Eagle Optics - Resource for Binoculars and Spotting Scopes for Birding, Hunting, Nature, Sports, and Outdoor Recreation. See Complete Online Binocular Catalog and Buying Guide.
http://www.eagleoptics.com/

Mike's Birding Blog - Reviews of optical equipment for birding and digiscoping. Articles and pictures about birding.
http://www.birddigiscoping.com/blog.html

WorldTwitch - Binoculars and Spotting Scopes for Birding - Comparison of popular binoculars and telescopes used by birders, with recommendations.
http://www.worldtwitch.com/optics.htm

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.
http://www.birdwatching.com/optics.html

Better View Desired - Birding optics reviews, articles, manufacturers, and retailers.
http://betterviewdesired.com/

All About Optics - Advice about selecting optics for birding and reviews of binoculars and spotting scopes. Sponsored by Eagle Optics.
http://www.allaboutoptics.com/

Audubon Society Guide to Binoculars - Guide to buying binoculars from the National Audubon Society.
http://www.audubon.org/bird/at_home/bird_watching/binoculars.shtml

Optics4birding - Sells binoculars, scopes, and tripods. Includes reviews, articles on optics basics and a buying guide.
http://www.optics4birding.com/

BirdScope - Information about birding with Tele Vue telescopes, with telescope and accessory selection guides, specifications, reviews, usage notes, and dealer list.
http://www.televue.com/birdscope/