tox . It makes testing of libraries that must run under multiple Python versions and implementations so much easier than it used to be. Not Python, but I've also come to respect Git and GitHub a lot this year.
The Pylons Project . I contributed mostly to the Pyramid web framework but also many other libraries in the project (WebOb, Deform, Colander, a bunch of Pyramid add-ons, etc). An obscene amount of time was spent hanging out in its related IRC channel.
Probably the Python subreddit. Always lulz going on there. I know it's ridiculous to read the comments there (much less respond), but it's like watching reality TV: you know it's a complete waste of time but sometimes you can't tear yourself away.
A Python packaging system to succeed setuptools + distutils that has wide support. And great docs.
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