Google Charts - Interactive charts for browsers and mobile devices.
Core Plot - Cocoa plotting framework for OS X and iOS
Highcharts - A charting library written in pure JavaScript, offering an easy way of adding interactive charts to your web site or web application
PNChart - PNChart is a chart lib used in Piner and CoinsMan for iOS.
ZoomCharts - Creating meaningful and aesthetically pleasing data visualizations and incorporating them into your projects is easy with the tools offered by ZoomCharts.
SwiftCharts - i-schuetz - Easy to use and highly customizable charts library for iOS