Haml is a layer on top of HTML or XML that is designed to express the structure of documents using indentation rather than closing tags. It was originally envisioned as a plugin for Ruby on Rails, but it can function as a stand-alone templating engine.

Puma is a simple, fast, threaded, and highly concurrent HTTP 1.1 server for Ruby/Rack applications. Puma is intended for use in both development and production environments. In order to get the best throughput, it is highly recommended that you use a Ruby implementation with real threads like Rubinius or JRuby.

Bond can autocomplete argument(s) to methods, uniquely completing per module, per method and per argument. Bond provides a configuration system and a DSL for creating custom completions and completion rules. Bond can also load completions that ship with gems. Bond is able to offer more than irb's completion since it uses the full line of input when completing as opposed to irb's last-word approach.

The Stud Ruby library adds a few things missing from the standard Ruby library such as:

Stud::Try

Retry on failure, with back-off, where failure is any exception.

Stud::Pool

Generic resource pools.

Stud::Task

Tasks (threads that can return values, exceptions, etc.)

Stud.interval

Interval execution (do X every N seconds).

Stud::Buffer

Batch and flush behavior.

This package is a collection of ANSI escape code related libraries enabling ANSI colorization and stylization of console output. Included in the library are the Code module, which defines ANSI codes as constants and methods, a Mixin module for including color methods, a Logger, a ProgressBar, and a String subclass. The library also includes a Terminal module which provides information about the current output device.

Mail is an internet library for Ruby that is designed to handle email generation, parsing and sending. The purpose of this library is to provide a single point of access to handle all email functions, including sending and receiving emails. All network type actions are done through proxy methods to Net::SMTP, Net::POP3 etc.

Mail has been designed with a very simple object oriented system that really opens up the email messages you are parsing, if you know what you are doing, you can fiddle with every last bit of your email directly.

Prawn is a pure Ruby PDF generation library.

Bacon is a small RSpec clone providing all essential features.

Ethon is a very basic libcurl wrapper using ffi.

ruby-hydra is a Ruby library for working with hyphenation patterns.

This package provides a parser for Ruby source code, written in C.

XPath is a Ruby domain-specific language (DSL) for generating XPath expressions.

This package provides a Ruby kernel for Jupyter/IPython frontends (e.g. notebook).

EXIF Reader is a module to read EXIF from JPEG and TIFF images.

Diffy provides a convenient way to generate a diff from two strings or files.

This library can read and update netrc files, preserving formatting including comments and whitespace.

Crass is a pure Ruby CSS parser based on the CSS Syntax Level 3 spec.

Erubi is a ERB template engine for Ruby. It is a simplified fork of Erubis

This package provides assorted command line tools that may be useful when working with Ruby code.

crack provides really simple JSON and XML parsing, extracted from code in Merb and Rails.

Open4 is a Ruby library to run child processes and manage their input and output.

nio provides cross-platform asynchronous I/O primitives in Ruby for scalable network clients and servers.

Ruby Rsync is a Ruby library that can synchronize files between remote hosts by wrapping the rsync binary.

This package provides a Ruby client that tries to match Redis' API one-to-one, while still providing an idiomatic interface.