One way to do a tiny amount of good in the world (assuming you shop on Amazon.com) is to opt in to Amazon Smile. Once you have done so, Amazon will donate 0.5% of the money you spend on the site to the charity you select. I’m set up to donate to the Environmental Defense Fund currently. The catch is that for the donation to be applied, you have to access the site through “smile.amazon.com” rather than “www.amazon.com.” Amazon will remind you of that a few times, but then it goes away, and of course when you follow links to Amazon, they’re always to the main URL.
Fortunately, there are browser plugins that will make sure you’re always browsing through smile.amazon.com. For Firefox, there’s Amazon Smile Redirector. For Chrome, there’s Smile Always. It looks like a version of Smile Always for Safari is under development, but it’s not available in Apple’s extension gallery. If anyone knows of such an extension for Safari, post in the comments and I’ll add it.
Unfortunately, this seems to be a US-only program currently. Hopefully Amazon will expand it to other countries eventually.