My primary frontend blog/website (https://www.impressivewebs.com/) is mostly passive, I post maybe one article per month, usually not even that much. The blog has been active for about 10 years, so I get lots of SEO traffic, which brings in about $400-500 per month.

I also sell ebooks that are compilations of articles and tips from my newsletter (see below) on Leanpub and Amazon. (https://leanpub.com/b/javascriptdombundle)

My main newsletter (https://webtoolsweekly.com/) is now also a regular income stream (about $400-700 per month and growing), but not exactly passive. Takes regular research, writing, etc. But it’s fun to do and leads to all sorts of paid tech writing projects.

Finally, my newest newsletter (https://techproductivity.co/) is not yet making money but that’s starting to change as the subscription number has started to rise to a decent number and it’s very easy to write that one, maybe 2 hours of work per week.