I found d3.js a few years ago and thought it was absolutely brilliant. I immediately wanted to use it for plotting data (something I do a lot, but have never been happy with my many options: Gnumeric/Excel, QtiPlot/Origin, matplotlib/Matlab, and Octave/Gnuplot).
The one problem was d3.js is a data visualization library, not a graphing/plotting/charting library, and the typical charts I generate require building up the components from scratch.
I played around with it a good amount and read some amazing posts about it. Following the example from the author/creator of d3.js, I set about making “reusable charts” that did a lot of the [admittedly simple] task of simple x/y line charts.
My goal is to use this for some of my work and add to and improve as I experiment and use it more.