Below are a few links that you may find useful.

PlanetCatfish - THE Aquarium catfish website

UK Aquarist Classifieds - A must for anyone based in the UK

Urban Philosophy - Perfect If you Live in the Netherlands, and need someone to feed your fish whilst you're on Holiday

Tropical Fishfinder - Based in the UK great deals and a useful resource

Aquarium Electrical Systems - Very informative

Scotcat - Another fantastic resource and of course, it's Scottish - Not in English but can be translated in Google

Fishaholics - A fantastic and very friendly site run by our very own Barbie!

Aquaauction - The UK's First Online Aquatic Auction Site

Corydorasworld - What else can I say!