The Ruby on Rails web framework. There are a lot of issues being tracked in github leading up to the 4.0 release.
Open Source multi-language/multi-currency/multi-store eCommerce platform
The Rails application that powers OpenStreetMap
🍻 A CLI workflow for the administration of macOS applications distributed as binaries
A pure Ruby code highlighter that is compatible with Pygments
A platform for community discussion. Free, open, simple.
:gem: A fast, open source text processor and publishing toolchain, written in Ruby, for converting AsciiDoc content to HTML 5, DocBook 5, and other formats.
Git repository of MarkUs
Crowd sourced code reviews on practice problems in ruby, javascript, python, objective c, haskell, elixir, clojure, or scala. More languages in the works.
Classy web-development dressed in a DSL (official / canonical repo)
Simple, efficient background processing for Ruby
Server automation framework and application
A simple, Git-powered wiki with a sweet API and local frontend.
Exercism is a community around crowd-sourced code reviews. The core is in Ruby but exercises appear in all languages.
A Ruby gem for communicating with the Twilio API and generating TwiML
Vagrant is a tool for building and distributing development environments.
Metasploit Framework