Hi Mr Grimwig...
My name is Diana Troth and I used to volunteer many years ago (in the 80's) at one of our local shelters and worked for one of the veterinarians who volunteered his time for them as well.
There are a few things you can do to help that won't cost you but a phonecall and maybe a little bit of gasoline.
Many shelters will let people volunteer to take the animals out of their cages and go for a daily walk or play with them in the shelter's "yard" if they have one.
Also, you can take your shredded paper to the animal shelter in the winter and they may use it for the animals bedding and warmth from the concrete floor. Also, any old, but clean, blankets you may wanna get rid of are almost always accepted by the shelters too...again, for the winter months.
You can go on a one man (or invite all of your friends and family to help you) spey and neuter campaign to help people learn the consequences of letting their animals continually have babies. That's the main reason why "MILLIONS" of innocent animals are killed in the "shelters" and pounds each and every single year across the United States.
Some shelters and maybe even some pounds will let you "foster" an animal where they will provide the animals food, vaccinations, de-worming etc and all you have to provide is the love and time and of course, the temporary home. Not all shelters are this progressive though, but it won't hurt to ask them if they'd be willing.
Good luck with your endeavor! (:
May peace and love and caring remain in your kind and gentle heart and soul...always,