I’ve added a module directory to /home/deploy/host-addons. Starting up Odoo definitely knows about it:

2014-09-08 10:50:08,533 5198 INFO ? openerp: addons paths: ['/home/deploy/odoo/local/data/addons/8.0', u'/home/deploy/odoo/build/8.0/openerp/addons', u'/home/deploy/odoo/build/8.0/addons', u'/home/deploy/host-addons']

There's nothing strange in the addons folder:

$ ls -dl /home/deploy/host-addons/**/*
-rw-r--r-- 1 vagrant vagrant  24 Sep  8 03:30 /home/deploy/host-addons/test/__init__.py
-rw-r--r-- 1 vagrant vagrant 275 Sep  8 03:31 /home/deploy/host-addons/test/__openerp__.py

The contents are from the example at: http://odoo-80.readthedocs.org/en/latest/howtos/website.html

==> /home/deploy/host-addons/test/__init__.py <==
__author__ = 'kitsunde'

==> /home/deploy/host-addons/test/__openerp__.py <==
# -*- coding: utf-8 -*-
{
    # The human-readable name of your module, displayed in the interface
    'name': "Academy",
    # A more extensive description
    'description': """
    """,
    # Which modules must be installed for this one to work
    'depends': ['base'],
}

Why isn't Odoo picking up my module?