Before I got the job I have now, I did some volunteer work for a local charity that helps homeless folks transition to getting affordable housing. I answered phones and did some other things. I even served on the board of directors for a while. That was a fun thing to do as I looked for work. Volunteering is a good way to keep skills sharp and to give back.
At my church, I serve during the worship services as a communion assistant and as a live video streaming and sound tech. I have also served on the leadership team known as the vestry.
So I would guess I would do things for free that I feel passionate about and that can make a difference.