Meetup - Helps groups of people with shared interests plan events and facilitates off line group meetings in various localities around the world.
GitBook - Modern Publishing, Simply taking your books from ideas to finished, polished books.
Event Hunt - Startups and Tech Events Curated By Locals
MkDocs - Project documentation with Markdown.
Eventbrite - Discover Great Events or Create Your Own & Sell Tickets
Docusaurus - Easy to maintain open source documentation websites