Ask HN: How and where to mentor people new to programming?

I've been thinking about the ways I could contribute to the industry and a few options immediately pop up: open-source projects, writing blogs or articles, but I think one of the ways of contributing isn't talked about that much - simply mentoring or helping out less experienced programmers. There are obvious problems with mentoring since you can do more harm than good to someone who is barely starting. Does anyone have any experience of doing this in an environment outside of work? I've spent long hours helping colleagues with code issues and mentoring interns or graduates, so I hope I can take a step in a different direction.