Chartkick is a Ruby gem (also has a JavaScript API which doesn’t require Ruby) for creating good-looking charts very easily and quickly. It integrates with 2 charting libraries: Highcharts and Google Charts where it is possible to use the same functions for generating charts with each library.
There is support for multiple chart types and multiple series in a single chart. And, like mentioned there is also Chartkick.js which brings the same functionality to the client-side, without Ruby.
Requirements: Rails 3.1+ (for the Ruby version)
Website: http://ankane.github.io/chartkick/
Download: https://github.com/ankane/chartkick
