Ruby on Rails is an open-source web application framework for the Ruby programming language. The growing demand for Ruby on Rails has been driven by successful companies who benefit from the speed and agility of building applications in Rails, which results in increased productivity and company growth. Many of the companies you all know and love use Ruby in some capacity: Amazon, BBC, Cisco, CNET, IBM, JP Morgan, NASA, and Yahoo!. Many of the fastest-growing web-based companies have been built using Ruby on Rails: Scribd (over 70 million readers each month), Groupon (over 38.5 million subscribers in North America), Basecamp (millions of users). All in all, more than 200,000 web sites are using Ruby on Rails.