This gem assumes you're using Rails 3.1+, including the asset pipeline.
Into the Gemfile:
gem 'css3-progress-bar-rails'
Into the application.css header:
*= require 'css3-progress-bar'
In a view:
<%= progress_bar(33, :color => 'blue', :rounded => true) %>
Twitter Bootstrap Flavored (may not fully work with current version)
<%= bootstrap_progress_bar(33, :color => 'info', :striped => true) %>
Except where indicated: Copyright (c) 2017 Nicholas Fine, released under the MIT license.