Grafico is a javascript charting library built with Raphaël and Prototype.js. The library provides a wide array of graphs and stays with the guidelines laid out by Stephen Few and Edward Tufte. Grafico provides pretty charts that effectively communicate their information.

This means you get awesome graphs such as stacked area charts and sparklines, but no pie charts or bar charts with every bar a different color. Each graph type has numerous API options to customize it’s look and behavior. Some highlights: pop-up hovers, meanlines and watermarks. Minified, Grafico is about 30kb and available under the MIT license.

Requirements: Raphaël and Prototype.js
Demo: http://kilianvalkhof.com/2010/design/grafico-javascript-charting-library/
License: MIT License