Epinions: Speakers
Consumer-generated reviews, buying tips and advice, ratings, price information, and searchable in a variety of ways from price to product type.

ReviewCentre.com: Speaker Reviews
Consumer reviews on speakers.

eBuying Guides: Where to Buy Speakers/Headphones
Concentrates on where to shop for products, but also has staff-produced buying guides. Some of the guides are links to other buying guide sites.

Dooyoo.co.uk: Speakers
Consumer opinions, reviews and ratings.

Epinions: Computer Speakers
Comparisons and reviews written by consumers.

Stereo Speaker Buyer's Guide
Features select lists of stereo speaker best values based on positive media reviews and awards. Includes buying, upgrading, repairing, diy, tweaking and setup tips.

Subwoofers - What You Need To Know
Explains types, crossovers, alternatives, shopping and installation tips.

Bryce's Speaker Building
Information about building speakers for DIY projects.

High Efficiency (Exponential) Loudspeaker Set For Disco Application
Physics principles, calculations, drawings, specifications, pictures, and internet resources/references. PDF version of the site available as well.