- Bundler - Bundler maintains a consistent environment for ruby applications. It tracks an application's code and the rubygems it needs to run, so that an application will always have the exact gems (and versions) that it needs to run.
- rabl - General ruby templating with json, bson, xml, plist and msgpack support
- Thin - Very fast and lightweight Ruby web server
- Unicorn - Unicorn is an HTTP server for Rack applications designed to only serve fast clients on low-latency, high-bandwidth connections and take advantage of features in Unix/Unix-like kernels.
- SimpleCov - SimpleCov is a code coverage analysis tool for Ruby 1.9.
- Zeus - Zeus preloads your Rails app so that your normal development tasks such as console, server, generate, and specs/tests take less than one second.
- factory_girl - factory_girl is a fixtures replacement with a straightforward definition syntax, support for multiple build strategies (saved instances, unsaved instances, attribute hashes, and stubbed objects), and support for multiple factories for the same class (user, admin_user, and so on), including factory inheritance.
- Sass - This gem provides official integration for Ruby on Rails projects with the Sass stylesheet language.
- ActiveAdmin - Ruby on Rails plugin for generating administration style interfaces
- Delayed::Job - Database based asynchronous priority queue system -- Extracted from Shopify
- Resque - Redis-backed Ruby library for creating background jobs, placing them on multiple queues, and processing them later.
Tools and Services
- Heroku - Hosting provider for Ruby, Node.js, Clojure, Java, Python and Scala
- Forward - Forward your localhost to a publicly-accessible url
- Mandrill - Transactional email based on MailChimp infrastructure
- Jenkins - Open source continuous integration server
- Ruby on Rails Guides - These guides are designed to make you immediately productive with Rails, and to help you understand how all of the pieces fit together.
- Better Specs - Collection of "best practices" that other developers learn through years of experience.