Adopt-a-Pet - http://www.adoptapet.com/ An online non-profit charity that helps advertise homeless animals and other great things.
NetPets.org - http://www.NetPets.org A site that helps find information on finding homes for animals, or adopting animals in need.
PetBond.com - http://www.petbond.com A site that helps you show your adoptable rescues, post your information, etc.
Petfinder.com - http://www.petfinder.com A wonderful place to find information on rescues and shelters, find animals for adoption, and meet other people who are doing the same.
Alley Cat Allies - http://www.alleycat.org A place to find information about stray/feral cats and how to help them.
American Humane Assocaition - An organization dedicated to helping and protecting animals
Animal Legal Defense Fund – ALFD - Protects the lives and advances the interests of animals through the legal system.
Animal Protection & Rescue League - Works to document and expose animal cruelty occurring behind closed doors, educates the public on animals issues through innovative outreach campaigns, and works with policymakers and politicians to implement humane change.
Last Chance for Animlas - Primary focuses are vivisection, pet theft, fur, and circuses.
Dogs Deserve Better - a 501c3 nonprofit organization dedicated to freeing the chained dog
Doris Day Animal League - http://www.ddal.org Mission is to reduce the pain and suffering of non-human animals through legislative initiatives, education, and programs to enforce statutes and regulations which have already been enacted protecting animals.
Humane Farming Association - http://www.hfa.org . - HFA's goals are to protect farm animals from cruelty and abuse, to protect the public from the misuse of antibiotics, hormones, and other chemicals used on factory farms, and to protect the environment from the impacts of industrialized animal factories.
Humane Society Legislative Fund - http://www.fund.org HSLF works to pass animal protection laws at the state and federal level, to educate the public about animal protection issues, and to support humane candidates for office.