As readers of the website might know, I am an avid enthusiast and follower of the FI/RE movement (e.g., Financial Independence, Retire Early). If you want to read more about that, I suggest starting with this article here and follow it up with more of my favorites here.
There has been a complimentary theory that has started to revolutionize charitable giving that many FI/RE proponents have endorsed that is called Effective Altruism. The gist of Effective Altruism is that if you truly believe all lives are equal then you should focus your giving towards having the most impact with regards to saving lives. Oftentimes, this means donating towards health-related organizations that operate in under-developed countries as each donated dollar tends to go farther in those places.
Singer has also set-up a website at https://www.thelifeyoucansave.org/ that encourages people to pledge towards Effective Altruism and highlights charities that tend to provide the most benefit for the donated dollar. My wife and I chose to donate our funds towards the Fistula Foundation, but you can take a look at other suggested charities here.
If you have the means, I highly encourage doing your own research about effective altruism (that includes reading-up on some of the nay-sayers as well) and come to your own conclusions on how and where to give.