The best Rails 4.2+ forums engine ever. Its goal is to be as simple and feature rich as possible. Thredded works with SQLite, MySQL (v5.6.4+), and PostgreSQL. See the demo at https://thredded.org/.

Command line tool for viewing Markdown files (with GitHub Markdown extensions) in a browser

Generic components from jeromegn/DocumentUp for generating static HTML documentation from Markdown.