lol_dba is a small package of rake tasks that scan your application models and displays a list of columns that probably should be indexed. Also, it can generate .sql migration scripts.

Hooks Roadie into your Rails application to help with email generation.

XML parameters parser for Action Pack (removed from core in Rails 4.0)

Link header pagination for Rails and Grape APIs

Chosen is a javascript library of select box enhancer for jQuery and Protoype. This gem integrates Chosen with Rails asset pipeline for easy of use.

PostgreSQL JSONB-based model changes tracking

Easy upload management for ActiveRecord

The minitest-spec-rails gem makes it easy to use the \ Minitest::Spec DSL within your existing Rails test suite.

Lookbook is a UI development environment for Ruby on Rails applications

Use your angular templates with rails' asset pipeline

jQuery plugin for drop-in fix binded events problem caused by Turbolinks

A Rails engine for queuing and managing maintenance tasks

Haml-rails provides Haml generators for Rails 3. It also enables Haml as the templating engine for you, so you don't have to screw around in your own application.rb when your Gemfile already clearly indicated what templating engine you have installed. Hurrah.

Deface is a library that allows you to customize ERB, Haml and Slim views in a Rails application without editing the underlying view.

A thin wrapper to use Rails Migrations in non Rails projects

A wysiwyg text editor for Bootstrap

Adds methods to ActiveRecord::Migration to create and manage database functions and triggers in Rails

A plugin for versioning Rails based RESTful APIs.

The library allows you to easily build datagrid aka data tables with sortable columns and filters

Integration between Ember CLI and Rails