Earlier quoted context omitted.
You can also donate your time.
Well, if you're working in paid employment it will usually be a lot more effective to put in some more time at work, and give away some of the resulting income. "Donating your time" can of course be genuinely worthwhile if you're, e.g. a scientist who might want to do useful research on globally-relevant, critical issues; just not very much otherwise.
[0] https://youth.gov/youth-topics/mentoring/benefits-mentoring-...