Some months ago I ran a series of articles on “How to be a Birder.” Included in that series was one article about choosing binoculars. I’ve recently come across a good explanation of how binoculars work and how to choose those that will suit you. This advice is in the form of a downloadable file called “Choosing Binoculars for Birdwatching” from the Bird Observers Club of Australia (BOCA) [Update: sorry – that link no longer exists.]
Useful links:

• How to be a Birder – some hints.

• How to be a birder – Part 3 – Buy some binoculars.

UPDATE: More recently I found the following website with some very useful hints on choosing binoculars for birding: Optics Planet. This is a commercial site selling a wide range of optics for all kinds of activities. I am not endorsing the store, just the section on choosing binoculars.

UPDATE November 2013: some links on this post not longer exist. Sorry about that.