Ask HN: Experienced engs, how are you finding better opportunities (passively)?

I posted this yesterday: https://news.ycombinator.com/item?id=33783313

Piggybacking off of that, if you're an experienced (mid-level & beyond) eng, where are you going to check out new opportunities passively? Are you just depending on recruiters reaching out?

Are there any platforms or mailing lists one can sign up to anonymously keep tabs on interesting opportunities? Also, what about a new opp draws your attention (aside from total comp :D)