Sass - Syntatically Awesome Style Sheets
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.
PostCSS - Increase code readability. Add vendor prefixes to CSS rules using values from Can I Use. Autoprefixer will use the data based on current browser popularity and property support to apply prefixes for you.
Chart.js - Easy, object oriented client side graphs for designers and developers.
Stylus - EXPRESSIVE, DYNAMIC, ROBUST CSS
Google Charts - Interactive charts for browsers and mobile devices.