custom_counter_cache

PaperTrail

Track changes to your rails models

FriendlyId

FriendlyId is the “Swiss Army bulldozer” of slugging and permalink plugins for ActiveRecord. It allows you to create pretty URL’s and work with human-friendly strings as if they were numeric ids for ActiveRecord models.

AASM

AASM - State machines for Ruby classes (plain Ruby, ActiveRecord, Mongoid, NoBrainer, Dynamoid)

ActsAsTaggableOn

A tagging plugin for Rails applications that allows for custom tagging along dynamic contexts.