This is easily among the most active of all core CPython developers. His productivity is ridiculous, and I seriously wonder how he manages to do all he does, especially since he does it in his free time. He also tends to be quite stern, which is extra kool since he does it while displaying great depth of knowledge and maturity. Also, his great work has been officially recognized by the Python Software Foundation.
The first work that prompted this recognition as developer of note is the proposal, PEP 413. The idea is that the Python standard library (stdlib) should release at a quicker rate than the Python language itself. This is a nice balance between two camps: those favoring stability over quicker availability of features, and those favoring the opposite. The PEP (Python Enhancement Proposal) is quite thorough, and is partly in opposition to the earlier PEP 407, which proposes that all of CPython (the language and its stdlib) should release faster. Nick Coghlan outlines the disadvantages with that approach in PEP 413 as well.
Another PEP he is working on is PEP 432. Titled Simplifying the CPython startup sequence, it's a highly detailed proposal to re-organise some of CPython code to ease maintenance. His deep knowledge on the project's internals is also on display.
Nick also builds and maintains a collection of notes known simply as Nick Coghlan's Python Notes. There is much wisdom there (complete with high quality clear writing), favorite of which is the just-updated Incremental Plans to Improve Python Packaging, a thorough write-up on the history, current state, and future plans regarding the story of packaging (and installation) in the Python ecosystem. He also happens to be a great champion in pushing for progress on that front.