See if volunteers are needed at your local shelters. Some need dog walkers, help with feeding the animals, brushing the pets, etc.
You can also raise funds for the shelter by planning a bake sale or a car wash to donate the money for shelters.
Another way is to collect things that shelters need like blankets, toys, newspaper, and anything else beneficial to give to the shelter.
When someone wants to adopt a pet, tell them to check out the shelter pets.
Go to your local animal shelter and ask them if they're needing volunteers.