I volunteer at Pet Harmony, a one-of-a-kind pet supply store that is a solid base for Animal Compassion Network.
At Pet Harmony, we have dogs up for adoption in the back, and cats up for adoption off to the side in the front. All (absolutely every single 100% cent) proceeds from sales of the items go back to ACN and the store/adoption center combo.
We have a strict 3 step adoption-screening process, which means, obviously, that more people can get turned down than can be approved. We do multiple home-inspections as part of that process, too.
As for my part, I am an animal care volunteer. I do anything from walking the dogs and playing with the cats, to laundry and dishwasher maintenance (we always have to keep a cycle going because there is hardly ever nothing to be washed or dryed

). So basically, I do a wide range of things there.
My family is a member of the Humane Society of the United States, and of the ASPCA. Also at Pet Harmony, I donate cat and dog food that my own cat and dog have not finished when I switch them over to another kind.
Although we don't really have any room for guinea pigs to be a part of our rescue clan indoors where piggies need to be, I plan on suggesting the idea to them this weekend, the next time I'll be going there.