My Smart Puppy (Brian Kilcommons' site, author of Good Owner, Good Dog) - check out the LIBRARY in the bottom left corner for some excellent articles on behavior problems.
Volhard Puppy Aptitude Test (used to temperament test puppies BEFORE purchase, to be used with the book Dog Training For Dummies by Jack & Wendy Volhard)
Cat Fence-In containment system to keep your cat in your yard
Invisible Fence for cats and dogs
Slow down, you eat too fast; gotta make the moment last - An excellent article on how to keep your dog busy while he's eating, and to SLOW DOWN the eating process. Great for those whose dog's eat an entire meal in 7.3 seconds.
Dendrobatids (poison dart frogs) and vivarium construction
Pet health information
Zoonotic diseases - Appropriately called "Worms and Germs", it's a veterinarian's blog (from the Ontario Veterinary College) about the things that you can get from your pet, and how to avoid them. Great for all pet owners, especially those with two-legged children.