Perhaps your only issue with adopting is that you can’t take on a life-long commitment right now, but you are able to take on an animal for a short period of time. Then fostering is perfect for you! Some animals really suffer in a shelter, and require a more home-like environment to stay mentally healthy and happy. You only foster an animal until a permanent home is found for them, so there is no life-long commitment. Furthermore, you would actually be helping two animals, as fostering an animal will open up a spot in the shelter for another animal to be rescued and rehomed.
Educate your friends and family on the importance of things such as spaying and neutering, and how this can lower the number of unwanted and homeless animals, thus helping the shelter animals' plight.