Petfinder
Petfinder is one of the most well-known websites for pet adoptions. It allows users to search for adoptable pets, including cats, from various shelters and rescue organizations across the United States.

Adopt-a-Pet
Adopt-a-Pet.com is another large pet adoption website that connects potential adopters with animals in need of homes. Users can filter their search by location, breed, age, size, and gender to find the perfect cat for their household.

The Shelter Pet Project
The Shelter Pet Project is a collaborative effort between the Humane Society of the United States, Maddie's Fund, and the Ad Council. It promotes the adoption of pets from shelters and includes a searchable database of available pets.

Rescue Me!
Rescue Me! is part of a larger network of animal rescue websites. It specifically focuses on connecting adopters with cats that need homes and allows users to search by state for a variety of breeds and ages.

Best Friends Animal Society
Best Friends Animal Society operates the nation's largest sanctuary for homeless animals and provides adoption services. Their website offers a searchable database of pets available for adoption from their sanctuary as well as from other shelters and rescue organizations nationwide.

Chewy
Best known for its wide range of pet supplies and products, Chewy's adoption service complements their mission by connecting pets in need with loving homes.