I am quite surprized how few people are proposing to make art or music. Is this why artists/musicians can't make money, because so few people enjoy it? I always thought it was the digitization and easy access that allowed us to enjoy these things from our homes (instead of going out to clubs), but maybe not.
Anyway, for the record, I would be recording my lifetime backlog songs I've written. And probably re-recording in different styles. And perfecting every one, no more of this 'good-enough' demo stuff. I'd get all the needed gear and software, and have no more excuses. I've actually already started to do this, at the detriment of my actual career...sigh.
EDIT: now that I read the OP's question more closely, I guess the answers are skewed towards practical things that would make the world better...but impractical things like creative music and abstract art also make the world better, so I'm sticking with my plan!