There are a variety of organizations that strive to end animal abuse. Each group has a different focus, but their ultimate goal is the same: helping animals live safe and healthy lives.
Humane Society of the United States: One of the oldest and most respected animal welfare organizations, it does not operate shelters (despite the name "humane society," also used by many local rescue groups), but instead uses its considerable wealth to fight animal abuses and educate the public about proper treatment of animals. Initiatives include lobbying against animal abuse in filmmaking and TV production, urging governments to include animals in disaster planning and working to eliminate unsporting hunting practices.
American Society for the Prevention of Cruelty to Animals (ASPCA): This organization focuses primarily on the protection of companion animals. Its activities include a pet poison-control hotline, education efforts to raise standards in shelters and the Humane Law Enforcement division, which has investigatory powers in New York state.
People for the Ethical Treatment of Animals (PETA): Perhaps the best-known of the activist animal-rights organizations, it promotes the idea that animals are neither property nor food, and works to end factory farming, fur farming, hunting, fishing and the use of animals in clothing. It has been criticized for, among other things, the use of Holocaust imagery in its advertising.
Local animal shelters: In some areas, shelter officials have some investigatory and enforcement powers in animal cruelty cases. They may also be active in lobbying for legislation protecting animals.
Local police: Many departments have one or more animal control officers.
If you're passionate about ending animal abuse, consider joining one of these organizations.