This site is also linked to other sites that you can click on to donate to other charities as well.
http://www.freekibblekat.com/ and http://www.freekibble.com are also donation sites. Freekibblekat donates to shelter cats, and freekibble donates to shelter dogs. All you have to do is answer a trivia question, it doesn't matter if you answer wrong or right, they donate kibble either way. If you get it wrong or if you're just guessing, it's fun for educational purposes and helping animals. There's also a link here: http://www.freekatlitter.com/ you can click to donate cat litter to shelters for cats on the sites as well. (Both are related, and will even link you to the site by saying "click here to feed cats too" or "click here to feed dogs too."
So if you don't make a lot of money or have the time to volunteer at shelters, at least this is a small way to help animals. If you love animals, pass this on.
Also, you can buy stuff on the animal rescue site and the money goes towards the shelter animals as well. This isn't required, but they do have some nifty stuff on there.
Just thought I'd share for us animal lovers out there!