Code modularization, achieved in one way or another, is a technique a good developer must aim for because it helps keeping things small, well-tested and organized. And of course, it follows the DRY directive. So as a Node.js developer (and maybe contributor to the Open Source), creating and publishing an NPM module is one of those steps you will eventually face.
Probably if any Node.js developer would have to pick an indispensable tool of the ecosystem, npm would win by far.
The Node.js ecosystem is quite young and prolific: new tools appear almost every day or week, changing and turning upside down your current workflow, always trying to squeeze a little more productivity to your time and effort or simply making your work easier.
As an example, take a look on the NodeFramework page, where Azat Mardanov (@azat_co) collects lot’s of frameworks and utilities related to Node.js. Or NodeWebModules, more web oriented than the previous one, from Caio Ribeiro Pereira (@crp_underground).