The most frequent question I get asked about my acts_as_versioned plugin is How do you version associations? I have no desire to open that can of worms unless I absolutely need it in a project. "Richard Livsey":http://livsey.org decided he needed this feature, and created "acts_as_versioned_association":http://livsey.org/articles/2006/06/08/acts_as_versioned_association-plugin.

class Article < ActiveRecord::Base
  has_many :images
  has_and_belongs_to_many :categories

  acts_as_versioned
  acts_as_versioned_association :images
  acts_as_versioned_association :categories
end