OpenIdAuthentication is depend on gem ruby-openid 1.1.4. In addition, ruby-openid 1.1.4 is broken with 1.0.1 gem :(
So, I applied patch(Ticket#10604) and they works well.

0. Install gem ruby-openid(2.0.4)
   shell>>
   gem install ruby-openid
   <<--

1. Install plugin
   shell>>
   $ ./script/plugin install http://svn.rubyonrails.org/rails/plugins/open_id_authentication/
   <<--

2. Apply patch

• Get a patch and save as ticket10604.diff

http://dev.rubyonrails.org/ticket/10604

• Move diff file to plugin root
  shell>>

#{RAILS_ROOT}/vendor/plugins/open_id_authentication/ticket10604.diff
<<--

• Move to plugin root and do patch command
  shell>>
  $ patch -p1 < ticket10604.diff
  patching file init.rb
  Hunk #1 FAILED at 1.
  1 out of 1 hunk FAILED -- saving rejects to file init.rb.rej
  patching file lib/generators/open_id_authentication_tables/open_id_authentication_tables_generator.rb
  patching file lib/generators/open_id_authentication_tables/templates/migration.rb
  patching file lib/open_id_authentication.rb
  Hunk #5 succeeded at 69 with fuzz 1 (offset -2 lines).
  Hunk #6 succeeded at 88 (offset -2 lines).
  Hunk #7 succeeded at 152 (offset -2 lines).
  patching file lib/open_id_authentication/association.rb
  patching file lib/open_id_authentication/db_store.rb
  patching file lib/open_id_authentication/nonce.rb
  patching file lib/open_id_authentication/setting.rb
  patching file tasks/open_id_authentication_tasks.rake
  patching file test/normalize_test.rb
  patching file test/open_id_authentication_test.rb
  patching file test/status_test.rb
  <<--

2. Do some work in README

• Creating tables
  shell>>
  rake open_id_authentication:db:create
  <<--

• Add some routes
  rails>>

#config/routes.rb
map.open_id_complete 'session', :controller => "sessions", :action => "create", :requirements => { :method => :get }
map.resource :session
<<--

• Generate SessionsController, and create vews/sessions/new.html.erb
  Tip:NOT to use sample code in agilewebdevelopment.com. Use sample code in README.
  rails>>
  def open_id_authentication
  authenticate_with_open_id do |result, identity_url|
  if result.successful? && @current_user = @account.users.find_by_identity_url(identity_url)
  successful_login
  else
  failed_login(result.message || "Sorry, no user by that identity URL exists (#{identity_url})")
  end
  end
  end
  <<--

3. Ommit version of ruby-openid
   rails>>

#open_id_authentication/init.rb
begin

gem 'ruby-openid', '=1.1.4'

gem 'ruby-openid'
<<--