Fineuploader is a Javascript plugin written by Andrew Valums, and actively developed by Ray Nicholus. This plugin uses an XMLHttpRequest (AJAX) for uploading multiple files with a progress-bar in FF3.6+, Safari4+, Chrome and falls back to hidden-iframe-based upload in other browsers (namely IE), providing good user experience everywhere. It does not use Flash, jQuery, or any external libraries.
This gem integrates this fantastic plugin with Rails 3.1+ Asset Pipeline.
gem 'fine-uploader-rails', '~> 3.2'
Require fineuploader in your app/assets/application.js file
//= require fineuploader
Fineuploader with JQuery wrapper
//= require fineuploader.jquery
Require the stylesheet file to app/assets/stylesheets/application.css
*= require fineuploader
Thanks to Andrew Valums and Ray Nicholus for this plugin.