How long since you last handwrote a letter on paper and sent it by post? Wanna get old school for a cause?
If you (or somebody you know) are a scientist (in any field, and including university students) you could write “letters to a pre-scientist”. That’s a project that turns scientists into pen pals of kids in USA areas with high poverty. The idea being that once you know someone in science, it’s easier to imagine yourself working in it in the future.
Applications for the coming school year are open and you can take a peek here.