Matplotlib
Yet another reason to learn Python is matplotlib, a matlab like system for creating plots, graphs, and charts. It seems a lot more of the style of system that one would want to use on the Web than say IllustRender :), at least for plots, graphs, and charts. Probably IllustRender would be a better system for general diagrams. I’m also planning to get that up and working here, so I can mess around with graphs. It’s already installed on the server, just needs a LaTeXRender-like frontend.