Low cost spay and neuter programs in conjunction with TNR (trap - neuter and release) activities have been shown to be the most effective way to address the many issues associated with the homeless cat population.
Hands Helping Paws is a local organization that does a phenomenal job of caring for feral cats in the Norman, Oklahoma area and engaging in TNR activities as well as finding homes for hundreds of kittens and cats. What is TNR? You can find out more by visiting the HHP link. I also found the following definition of TNR on the web:
TNR is a comprehensive plan where entire feral colonies are humanely trapped, then evaluated, vaccinated and neutered by veterinarians. Kittens and cats that are tame enough to be adopted are placed in good homes. Adult cats are returned to live out their lives under the watchful care of sympathetic neighborhood volunteers.
What is astonishing is that HHP found placement for so many using only a foster home network of dedicated volunteers...there is no shelter as such and all "housing" and fostering for the cats is provided by the volunteers. Last year they found homes for over 700 kittens and cats...amazing.
Kim Fairbanks, the founder and director, is a dedicated and tireless worker on behalf of homeless cats (and sometimes other animals) and she and the network of volunteers are terrific examples of what should be the norm in terms of how human animals relate to cat animals, especially those that are homeless and too wary to live with human companions. Visit the HHP facebook page to see photos of the cats and kittens needing homes and to learn more about their activities.
Seek out and support organizations in your area that support TNR activities and help them out however you can. Human animals created the homeless cat population and it is our responsibility to help the cat people suffering as a result of our carelessness.
Remember, you can reduce suffering for all our fellow animals by living as an ethical vegan.