This is a gem for Rails >= 3.1 applications. It provides all the basic DataTables files, but not (yet) the extras.
First, put the gem in your Gemfile (gem 'jquery-datatables-rails') and run bundle install
After installing it you can require it in your application.js file with //= require jquery.dataTables.min, or use the images and stylesheets in the dataTables directory: <%= image_tag 'dataTables/sortBoth.png' %>.
However, if you use the stylesheets include them separately and not compiled in the application.css.
This is because images in the stylesheets are referenced to without a path. So if you include the stylesheet dataTables/demo_table_jui it works, because the images are also under dataTables. But if you include the stylesheet in the application.css, it won't work.
Right now, the only plugin that is available is fnReloadAjax. Check out the assets directory.