Apache Software Foundation accepts individual donations of any amount that are tax-deductible: https://apache.org/foundation/individual-supporters

Outreachy is another excellent 501c3 that provides paid internships for open source: https://www.outreachy.org/sponsor/donate/

Let's Encrypt provides free TLS certificates to anyone: https://letsencrypt.org/donate/

You can find a wide range of OSS projects on OpenCollective: https://opencollective.com/search?q=&tag=open+source