The easiest place to find Labradors available for adoption is through a breed-specific rescue, which you can find by contacting the American Kennel Club or local Labrador clubs. You can also search for adoptable Labradors on PetFinder.com, which lists adoptable dogs from local shelters and rescues. This website allows you to create an ongoing search that tells you when a new dog matching your criteria is listed.
Labradors are a popular breed and are available from municipal shelters and all-breed rescues as well. Municipal shelters may have websites that list adoptable dogs, but it is usually better to visit them in person to look for dogs because some may not keep their website listings up-to-date due to lack of time and funding. Dogs typically pass in and out of city shelters fairly quickly, so visit regularly until you find a suitable dog.
Research each rescue organization thoroughly before deciding to adopt a dog from it to make sure it is a legitimate rescue. Some unethical breeders pretend to be rescues to sell their dogs more easily. PetFinder.com screens rescue groups, so organizations with listings on that site are typically legitimate. Reputable rescue groups spay or neuter and vaccinate their dogs before sending them home. Good rescue groups should also screen potential adopters thoroughly, so be wary of groups that do not seem interested in your qualifications for pet ownership.