Some things in nodejs need to be done synchronously (or, at least, shouldn't be enqueued at the rate a foreach loop will do so). Once I wrote this function three or four times, I decided it was time to put it somewhere easily accessible.

queue.js

/**
 * @file queue.js
 * This is an asynchronous queue for nodejs. Initialize it with a callback to 
 * execute against each item in the queue and (optionally) a queue of items 
 * against which to operate. Then, execute emitter.emit('next') at the end of 
 * your callback to trigger each subsequent run. Queue.exec() returns the 
 * emitter you'll need. Once exec has been called, each time push() is called, 
 * the pushed item will be execuated against at the end of the queue (if the 
 * queue is empty, it will be executed imediately).
 */

var events = require('events');

var Queue = function(callback, queue) {
	var _queue = queue || [];

	var _running = false;

	var _callback = callback;

	var _emitter = new events.EventEmitter();

	var _next = function() {
		if (_queue.length) {
			var item = _queue.shift();
			if (typeof(item) === 'array') {
				_callback.apply(this, item);
			}
			else {
				_callback.call(this, item);
			}
		}
		else {
			_emitter.emit('empty');
		}
	};

	_emitter.on('next', _next);

	return {
		push: function(item) {
			if (_queue.length === 0 && _running) {
				_queue.push(item);
				this.exec();
			}
			else {
				_queue.push(item);
			}

			return _emitter;
		},
		exec: function() {
			_running = true;
			
			for (var i = 0; i < 1; i++) {
				process.nextTick(_next);
			}

			return _emitter;
		}
	}
};

exports.Queue = Queue;