Codeigniter Mongo Queue is a plug and play addon to the Codeigniter framework
To use it, ensure that you have changed the settings in application/models/core_model.php to connect to the db of your choice.
You can add a job by calling enqueue in models/queue_model.php
Queue is called by running the queue function in controllers/queue.php from the command line.
Blog post for this project can be found here : http://blog.geeksphere.net/2013/03/01/implementing-a-queue-with-php-and-mongodb/