Broadway but smaller
Pluggo is a stupidly-named plugin library for Node.js and web browsers. You could also refer to it as a "dependency injection" or "inversion of control" library if you are feeling jaunty.
It's based on the parts of the broadway interface which I personally found myself using and functions more or less as a drop-in replacement.
It does not implement the detach function in broadway's plugin interface.
If you're using broadway in server code that you never plan on sharing with a browser, then you shouldn't.
If you're browserifying broadway though, you'll find that it clocks in at 243K, 56K when gzipped. Pluggo implements the same plugin interface with 0 dependencies and about 40 lines of code.
See broadway's API docs and pretend that the parts about detach and name aren't there. Congratulations, you have mastered Pluggo!