I agree with this and similar posts suggesting they find local non-profits. There's probably no perfect answer to what's most "efficient" and I think that's probably the wrong way to look at it. As a single, non-billionaire, there's only so much you can do to help others. But, you will get much more satisfaction from seeing "first-hand" the "effect of your actions". Sending your money to some faceless global charity is not going to be as rewarding and will make it a lot easier to stop doing.