The Data Visualisation Catalogue - Reference tool for data visualisation
D3.js - D3.js is a JavaScript library for manipulating documents based on data. D3 helps you bring data to life using HTML, SVG, and CSS.
Flourish - Powerful, beautiful, easy data visualisation
Chart.js - Easy, object oriented client side graphs for designers and developers.
nivo - nivo provides a rich set of dataviz components
Google Charts - Interactive charts for browsers and mobile devices.