There's always the Black Stallion series. This is the FIRST series, from the '60's/'70's. And the Margarite Henry books: Misty of Chinquotigue, Sea Star, King of the Wind - love those books. The illistrations were so beautiful. What wonderful memories. Another author who wrote some dog books is Albert Payson Terhune. Lad A Dog, Lad of Sunnybank, Buff: A Collie. Great books for kids (and adults who like to reminisce).
Thanks for bringing up some really nice memories for me!