Ask YC: Good People or Projects to Follow on Github

I've been noticing a bunch of interesting repos on Github lately, and not just of the RoR variety. I'm sure that a HN thread could turn up a bunch of great projects to follow. I'll start: Processing: http://github.com/jeresig/processing-js/ Python Plotting Library: http://github.com/astraw/matplotlib/tree/master Python Physics Tutorial: http://github.com/llimllib/bitofphysics/tree/master WYSIWYG Javascript: http://github.com/37signals/wysihat/tree