WP2Static - Static site generator for WordPress
Web Reactionz - Global reactions for the Web
GatsbyJS - Blazing-fast static site generator for React
DISQUS - Disqus is a global comment system that improves discussion on websites and connects conversations across the web.
Hugo - Hugo is a general-purpose website framework for generating static web pages.
Lyket - A tool to quickly add like/clap/vote buttons on a website