(I saw https://news.ycombinator.com/item?id=9305398 - the general advice in it is great; I was hoping to get an updated list for here in February 2018.)(Personally, I'd love to find smaller projects - it seems like a bunch of the projects listed in the earlier post are big things, such as Mozilla, Mercurial, Ruby)
(Side-question: I think this is a reasonable 'AskHN' topic, but if it's not I'd be happy to revise it and/or take it down).