RedCloth is a Ruby parser for the Textile markup language.

Rerun is a tool to launch programs, then monitor the file system, and restart the program when any of the monitored files change. It's written in Ruby, but can be used for all programs.

Slim is a template language for Ruby that aims to reduce the syntax to the minimum while remaining clear.

mkmf-lite is a light version of Ruby's mkmf.rb designed for use as a library. It does not create packages, builds, or log files of any kind. Instead, it provides mixin methods that you can use in FFI or tests to check for the presence of header files, constants, and so on.

RangeCompresses is a tiny library that allows compressing arrays of objects into arrays of ranges. For example, it can turn the following: [1, 2, 3, 4, 6, 8, 9, 10] into [1..4, 6..6, 8..10].

Ruby dubugging companion: pretty print Ruby objects to visualize their structure. Supports custom object formatting via plugins.

This package provides a Mocha adapter for Bacon, allowing you to use the Mocha stubbing and mocking library with Bacon, a small RSpec clone.

Colorator is a Ruby gem that helps you colorize your text for the terminal.

The Listen gem listens to file modifications and notifies you about the changes.

Tilt is a thin interface over a number of different Ruby template engines in an attempt to make their usage as generic as possible.

RubyPants is a Ruby port of the smart-quotes library SmartyPants. The original SmartyPants is a web publishing plug-in for Movable Type, Blosxom, and BBEdit that easily translates plain ASCII punctuation characters into smart typographic punctuation HTML entities.

HighLine provides a high-level IO library that provides validation, type conversion, and more for command-line interfaces. HighLine also includes a menu system for providing multiple options to the user.

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

Blather is a XMPP DSL for Ruby written on top of EventMachine and Nokogiri.

Oedipus Lex is a lexer generator in the same family as Rexical and Rex. It is based primarily on generating code much like you would a hand-written lexer. It uses StrScanner within a multi-level case statement. As such, Oedipus matches on the first match, not the longest.

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.

Systemu can be used on any platform to return status, stdout, and stderr of any command. Unlike other methods like open3 and popen4 there is no danger of full pipes or threading issues hanging your process or subprocess.

IRB is an interactive Ruby command-line tool for REPL (Read Eval Print Loop).

This gems add the --watch switch to the jekyll CLI interface. It allows Jekyll to rebuild your site when a file changes.

Namae (名前) is a parser for human names. It recognizes personal names of various cultural backgrounds and tries to split them into their component parts (e.g., given and family names, honorifics etc.).

RSpec::Its provides the its method as a short-hand to specify the expected value of an attribute. For example, one can use its(:size)\should eq(1)\.

ruby_version provides a RubyVersion module to simplify checking for the right Ruby version in software.

CukeModeler facilitates modeling a test suite that is written in Gherkin (e.g. Cucumber, SpecFlow, Lettuce, etc.). It does this by providing an abstraction layer on top of the Abstract Syntax Tree (AST) that the cucumber-gherkin generates when parsing features, as well as providing models for feature files and directories in order to be able to have a fully traversable model tree of a test suite's structure. These models can then be analyzed or manipulated more easily than the underlying AST layer.

Racc is a LALR(1) parser generator. It is written in Ruby itself, and generates Ruby program.