USDA Animal and Plant Health Inspection Service
Information on a variety of animal health related topics, including the latest news on such things as Mad Cow Diseases, foot and mouth disease, and many other things.

Heartworm Society
Everything you ever wanted to know about heartworm disease.

American Veterinary Medical Association
This site is a good starting point to learn more about a variety of topics, including feline injection-site sarcomas and the latest subjects in veterinary medicine.

Denver Dumb Friends League
Pet behavior information and advice.

Veterinary Partner
Answers questions about animal health, medications, therapies, surgery safety and behavior.