Our favorite websites:

Veterinary Partner (http://www.vspn.org/)
Database of articles on general veterinary care - unusually comprehensive and up to date.    

American Academy of Veterinary Nutrition (http://www.aavn.org)
This website has several good links for further information on nutrition.

American College of Veterinary Nutrition (http://www.acvn.org)
Shows list of all ACVN diplomates. 

National Research Council  - The 2006 Nutritional Requirements for dogs and cats, summarized
Dogs:  http://dels.nas.edu/resources/static-assets/banr/miscellaneous/dog_nutrition_final_fix.pdf
Cats: http://dels.nas.edu/resources/static-assets/banr/miscellaneous/cat_nutrition_final.pdf

Association for Pet Obesity Prevention - lots of education and tools for managing pet obesity
http://petobesityprevention.org/

Veterinary Botanical Medicine Association ( http://www.vbma.org/)
Professional association of veterinarians and herbalists trained and interested in herbal medicine. You can find a veterinary herbalist closest to you by searching the referral listing.

American Holistic Veterinary Medical Association ( http://www.ahvma.org/)
Umbrella organization for most holistic veterinarians.  You can find a holistic veterinarian closest to you by searching the referral listing.

American Association of Traditional Chinese Veterinary Medicine
Publisher of the American Journal of Traditional Chinese Veterinary Medicine ( http://ajtcvm.org/ )

American Academy of Veterinary Acupuncture (http://www.aava.org/)
American constituent of the International Veterinary Acupuncture Society. You can find a veterinary acupuncturist closest to you by searching the referral listing.

USDA Food Nutrient Database (http://www.nal.usda.gov/fnic/foodcomp/search/)
Search thousands of individual food items and prepared foods for calorie count and nutrient content

AAFCO Ingredient Definitions  (http://naturapet.com/tools/ingredient.asp?alpha=A)
From the Natura web site, definitions of all AAFCO feed ingredients found in pet foods.