Chart.js was first introduced in year 2013, for 3 years of intensive development by many contributors, it has became quite a powerful open source Javascript charting plugin.
It’s designed for both developers and designers. It supports 8 types of charts – Line, Bar, Radar, Polar Area, Pie & Doughnut, Scales charts. With version 2.0, you can mixed chart types, new chart axis types and animation support. Most importantly, it will play nicely with responsive layout.
Be sure to checkout the neatly organised documentation as well for introduction of each chart and example usage.