I nominate Lost Dog and Cat Rescue Foundation: http://www.lostdogrescue.org/ & Twitter: @lostdogrescue . Established in 2001 this non-profit organization saves the lives of thousands of homeless and abandoned pets each year. They rescue dogs and cats facing euthanasia in overcrowded shelters, and place them for adoption in loving homes. ALL of their animals are spayed or neutered prior to adoption. I have attended their adoption events several times and communicated with staff by phone and email, and all are very courteous and well informed.