Loading Notice is a plugin, built on Prototype, which shows an indictor when a slow AJAX is under process automatically. Basically, it's like the "Loading" div appears in gmail when busy. When scrolling or resizing the window, it will still keep showing on the top of the page.
Install the plugin:
$ ruby script/plugin install git://github.com/thomd/loading_notice.git
$ rake loading_notice:install
Include the library into your project:
<%= javascript_include_tag :defaults, 'loading_notice' %>
<%= stylesheet_link_tag 'loading_notice' %>
Use the loading-notice-demo template (for Rails >= 2.3) to generate a simple but fully functional proof-of-concept demo of the loading_notice plugin:
$ rails loading-notice-demo -m http://gist.github.com/156145.txt
$ ruby script/server
Minor enhancements by Thomas Duerr.
Original Plugin written by Shaokun Wu. Mail to shaokun at kudelabs.com for bug reports, feature requests or any comment.
Copyright (c) 2009 Kude Labs, released under the MIT license