I have over 200 modules on npm and over 400 projects on github. Most of these are just tiny things that solve some narrowly-defined long-tail problem but here are some of my more popular and interesting projects:
Use node-style require() calls to load scripts and npm modules in the browser.
Freestyle rpc. It's callbacks all the way down!
Transform source code on a recursive walk of the AST. This module is the basis for many of my source transformation experiments.
Turn any http server into a git endpoint that you can git push to.
Keep track of your services in a registry so that you can decompose your backend into lots of tiny services that all do just a single thing.
Parse command-line arguments.
Authenticate and encrypt with symmetric public keypairs across any kind of stream.