ruby script/plugin install http://svn.techno-weenie.net/projects/plugins/acts_as_draftable/

This example class will create drafts on the title and body fields of Article:

class Article < ActiveRecord::Base
  acts_as_draftable :fields => [:title, :body]
end

Here's a sample workflow:

1. Create your model.

article = Article.new(:title => 'foo', :body => 'bar')

2. Save draft.

article.save_draft

3. Retrieve latest draft.

draft = Article::Draft.find_new(:first, :order => 'updated_at desc')

4. Decide you like the draft, and save it.

article = draft.to_article
article.save
  
# notice your draft is now gone
Article::Draft.find_new(:first, :order => 'updated_at desc')
# => nil

5. Create a new draft from the saved article

article = Article.find(1)
article.title
# => 'foo'
article.title = 'bar'
article.save_draft

6. Load the draft's attributes over the current attributes without saving

article = Article.find(1)
article.title
# => 'foo'
article.load_from_draft
article.title
# => 'bar'

7. Save the draft's attributes over the current attributes

article = Article.find(1)
article.title
# => 'foo'
article.save_from_draft
article.title
# => 'bar'

There is currently no advanced documentation for this plugin.