I usually check ratings for a charity by reviewing it on Charity Navigator (which is itself a 501 (c) (3) and in need of donations as well). The rating for the Wikimedia Foundation happens to be really good: https://www.charitynavigator.org/index.cfm?bay=search.summar...

I use Wikipedia for reference on various topics on a daily basis and I know my kids do it at school as well. Hence, I donate to the Wikimedia Foundation, the approximate cost of my yearly Netflix subscription as they provide huge amounts of valuable information without any ads and to everyone without paywalls. There aren’t very many free services on the web that run without ads.