Ruby is a dynamic, reflective, object-oriented, general-purpose programming language.
It was designed and developed in the mid-1990s by Yukihiro "Matz" Matsumoto in Japan.
Here are Top 10 projects on github in Ruby:

1.devdocs

DevDocs is a web app aimed at providing you with quick access to the reference manual of just about every front-end language and library.
It lists all the APIs of a given selected language and their official documentation in an easily browsable and viewable format, without the needless menus and tacky attempted styling that official sites like php.net try to pull off.
It’s an Ajax-driven and open source web app with syntax highlighting, even available as a Chrome extension or as a plugin for Sublime Text or Brackets

2. Strong_migrations

　 Strong Migrations detects potentially dangerous operations in migrations, prevents them from running by default, and provides instructions on safer ways to do what you want.
Catch unsafe migrations at dev time.
This software is very important for detecting dangerous softwares.

3. Jekyll

Jekyll is a blog-aware, static site generator in Ruby.
Jekyll does what you tell it to do — no more, no less.
It doesn't try to outsmart users by making bold assumptions, nor does it burden them with needless complexity and configuration.
Put simply, Jekyll gets out of your way and allows you to concentrate on what truly matters your content.

4. Discourse

Discourse is the 100% open source discussion platform built for the next decade of the Internet.
Use it as a mailing list, discussion forum, long-form chat room, and more!
Discourse is a from-scratch reboot, an attempt to reimagine what a modern Internet discussion platform should be today, in a world of ubiquitous smartphones, tablets, Facebook, and Twitter.

5. rails

Rails is a web-application framework that includes everything needed to create databasebacked web applications according to the Model-View-Controller (MVC) pattern.
Understanding the MVC pattern is key to understanding Rails.
MVC divides your application into three layers, each with a specific responsibility.

• The Model layer
• The Controller layer

• The View layer

  6. metasploit-framework

  
  The Metasploit Framework is released under a BSD-style license.
  Metasploit can do all sorts of things.
  The first thing you'll want to do is start msfconsole, but after that, you'll probably be best served by reading Metasploit Unleashed, the great community resources, or the wiki.
  Bug tracking and development information can be found at:
  GitHub - rapid7/metasploit-framework: Metasploit Framework
  API documentation for writing modules can be found at:
  GitHub - rapid7/metasploit-framework: Metasploit Framework

  7. fastlane

  
  Fastlane is a continuous delivery tool for iOS and android apps.
  It started of as just an iOS delivery tool and therefore offers a much richer set of functionality for iOS apps.
  Fastlane itself is written in ruby and can be installed using ruby gems

$ gem install Fastlane

8. vagrant

Vagrant is a tool for building and distributing development environments.
Development environments managed by Vagrant can run on local virtualized platforms such as VirtualBox or VMware, in the cloud via AWS or OpenStack, or in containers such as with Docker or raw LXC.
Vagrant provides the framework and configuration format to create and manage complete portable development environments.
These development environments can live on your computer or in the cloud, and are portable between Windows, Mac OS X, and Linux.

9. thor

thor is a simple and efficient tool for building self-documenting command line utilities.
It removes the pain of parsing command line options, writing "USAGE:" banners, and can also be used as an alternative to the Rake build tool.
The syntax is Rake-like, so it should be familiar to most Rake users.

10. homebrew-cask

Homebrew-Cask extends Homebrew and brings its elegance, simplicity, and speed to the installation and management of GUI macOS applications such as Atom and Google Chrome.
We do this by providing a friendly Homebrew-style CLI workflow for the administration of macOS applications distributed as binaries.