It's not really working with them, but you can help them! You can donate things to shelters. Thats what I do. Donate things like blankets, towels, cat and dog toys, cat and dog treats, collars, pet beds, maybe cat trees and dog igloos, leashes, harnesses, pet grooming supplies, crates and carriers. Hope you take the advice! ;-)
Our shelter has a lot of little kids that when they have their birthday party they ask for dog and cat supplies. They then donate all items to our shelter. Call ur shelter and see what's their daily needs:)
Get a pet! Also, I volunteer at a farm near me, and I started when I was only 9. Maybe there is somewhere near you like that that needs your help? Riding lessons will also teach you how to work with horses. Also, there are plenty of summer camps that are located at farms where you will learn how to take care of animals.