Vinay Sajip is the maintainer of logging, a Python logging library/module, available in the standard library. What prompted this post is his tireless improvements, not just to the software itself, but also the documentation surrounding it (example). It's all the more impressive that he continuously blogs about various ways to use the module, and maintains a bunch of nuggets on advanced usage.
One early event, which is likely the first time I noticed him, is the time when he rebutted some apparently inaccurate claims against the module, at which he responded in a highly-detailed post, the sort that lent credence to the module. This inspired me to give it a try, and it's not that hard.
Lately, he is working on distlib, a library which implements low-level functions that relate to packaging and distribution of Python software. This excites me a lot since it's a key piece in the latest attempt at fixing Python packaging once and for all.
On top of all this, he is very active on Stack Overflow, having answered hundreds of questions there. Amazing!