Here you will find some of the sites I have found to be most useful & why.
Aquarium Stocking Calculator
Intelligent Saltwater Aquarium Stocking Calculator to help you setup correct stocks and filters for your aquariums and saltwater fish.
Reef hacks is a blog about saltwater and reef aquariums and they detail the various aspects of it as a hobby. They highlight the different issues common to saltwater and reef aquarium hobbyists, review the gear needed to help you decide if the latest product from your favorite brand is worth it or find alternatives and help you with other questions that you might have on the way to your successful reef tank.