Gives you a boolean reader/writer for a published_at (timestamp) column.

Add it to your Gemfile:

gem 'acts_as_published'

Install your bundle:

> bundle install

You need a published_at:timestamp column

In your model:

class Post < ActiveRecord::Base
  # acts as published
  include ActsAsPublished::ActiveRecord
  acts_as_published

  # ...
end

ActiveAdmin.register Post do
  form do |f|
    f.inputs do
      f.input :title
      # ...
      f.input :published, :as => :boolean
      # ...
    end
  end

  index do
    column :title
    # ...
    acts_as_published_columns
    # ...
  end

  show do
    attributes_table do
      row :title
      # ...
      acts_as_published_rows
      # ...
    end
  end  
end if defined?(ActiveAdmin)

You get following scopes:

Post.published
Post.unpublished