heatmap.js
JavaScript Library for HTML5 canvas based heatmaps
...Because it is the most advanced heat map visualization library on the web. It has a light footprint (~3kB gzip) and with the new 2.0 release heatmap.js just got faster and better. With only a few lines of code you can create your own interactive web heatmap. heatmap.js' API is all documented, also prioritized, so you can start developing right away! Heatmap.js is not a user behaviour tracking script. It simply creates dynamic heatmaps based on the data you feed it.