application.js

// Place your application-specific JavaScript functions and classes here
// This file is automatically included by javascript_include_tag :defaults

jQuery.ajaxSetup({  
  'beforeSend': function(xhr) {xhr.setRequestHeader("Accept", "text/javascript")}
});

jQuery.fn.submitWithAjax = function () {  
  this.submit(function () {  
//    $.post($(this).attr('action'), $(this).serialize(), null, "script");  
    $.ajax({
      type: $(this).attr('method'),
      url:  $(this).attr('action'),
      data: $(this).serialize(),
      dataType: "script"
    });
    return false;  
  });  
};

$(document).ready(function() {
  $("#chat_room_form").submitWithAjax();
})

chat_rooms_controller.rb

class ChatRoomsController < ApplicationController
  # ... all the action generated by script/generate: index, new, show, edit, destroy

  def send_data
    render :juggernaut => {:type     => :send_to_channels,
                           :channels => [params[:channel_id].to_i]} do |page|
      page["#chat_room"].prepend "<li>#{h params[:chat_input]}</li>"
    end
    #render :nothing => true
  end
end

I'd like to...

- use respond_to (or something else?) in send_data to externalize the .js processing, in the same fashion one would use a .rjs file.
- be able to use :method => "get" without triggering the show action.

send_data.js.erb

$("#chat_room").append('<li><%= escape_javascript("#{params[:chat_input]}") %></li>').fadeIn('fast').highlight;

show.html.erb

<%= javascript_include_tag 'jquery', 'json', 'juggernaut/juggernaut', 'juggernaut/jquerynaut', 'juggernaut/swfobject', 'application' %>
<%= juggernaut(:debug => false, :channels => [@chat_room.id]) %>

(id: <%= @chat_room.id %>)

<p><%= link_to 'Back', chat_rooms_path %></p>
<h1><%=h @chat_room.name %></h1>
<p><%=h @chat_room.description %></p>

<% form_tag({:action => "send_data"}, :method => "post", :id => "chat_room_form") do %>
  <%= text_field_tag(:chat_input) %>
  <%= hidden_field_tag(:channel_id, @chat_room.id) %>
  <%= submit_tag("Talk (JQuery with form_tag)") %>
<% end %> 

<ul id="chat_room" style="list-style: none"></ul>

<%= link_to 'Edit', edit_chat_room_path(@chat_room) %> |
<%= link_to 'Back', chat_rooms_path %>