node.js require cannot find custom module

The path is relative to the directory in which you are requireing the files, so it should be something like:

var couch = require('./couch');
var config = require('../config');

A bit of clarification, if you write

var couch = require('./couch');

you are trying to require the couch module which resides in the current directory, if you write

var couch = require('couch');

you are trying to require the couch module installed via npm.