I’m sure there are a number of generic online resources but i would love to hear what folks have fallen in love with?
When I was more invested in writing as a career, my favorite community was the AbsoluteWrite Forum. Mostly a good bunch of people, lots of solid advice and discussion. Is that the sort of thing you’re looking for?
I like gitbook.com - uses git for version tracking, very straightforward editor that uses Markdown for formatting and you can sync it with your Github account if you wish.