Although books are the best source of information for me, I have found quite a few magazines that have good articles and ideas. 

 ♥  Cat Fancy  I am not really into dogs but I am sure that Dog Fancy is just as good.  The only part I am not too   fond of is the breeders directory in the back. I wish there was a bigger concentration on shelter or rescue animals. 

♥  Animal Wellness

♥  Catnip- Tufts University newsletter- This has lots of great articles on everything cat.  I really enjoy reading Catnip. 

Book List

♥   The Merck/Merial Manual for Pet Health: The complete pet health resource for your dog, cat, horse or other pets - in everyday language. (Merck/Merial Manual for Pet Health (Home Edition)) by Merck Publishing and Merial, Cynthia M Kahn, and Scott Line

♥  Cat Owner's Home Veterinary Handbook, Fully Revised and Updated by Debra M. Eldredge DVM, Delbert G. Carlson DVM, Liisa D. Carlson DVM, and James M. Giffin MD

♥  The Pill Book Guide to Medication for Your Dog and Cat by Kate Roby and Lenny Southam (Paperback - Dec. 30, 2008)  This is a great book if you have an animal that needs to be on medication.  You can get good, easy to read information about common drugs.

♥  Dr. Kidd's Guide to Herbal Cat Care (Doctor Kidds Guides Ser. ) by Kidd, Randy

♥  The Complete Guide to Holistic Cat Care by Yarnall, Celeste, 2009, Quarry Books

♥  The Cat Fancier's Complete Cat Book by CFA and its associates, 2004, HarperCollins books (Not an advocate of breeding but I found this book to be useful about breed descriptions and it had a lot of other useful information)