Courtesy of Delta Hotels, so presumably to cities where they have a presence:

Enjoy exclusive discounts for travel until December 15!

Extra savings: up to 20% off your fall to popular Canadian cities. Get your discount simply by entering this promotion code when booking:

NB9W34Q1 - 20% off Executive Class fares
HFH7Y6N1 - 10% off Tango Plus and Latitude

Offer ends October 10, 2008.

About this offer:
* This offer is only available on new bookings and the discount applies exclusively on Air Canada published fares: Tango Plus, Latitude, and Executive fares and can not be combined with any other offer.

To take advantage of any of these offers, purchase your tickets at aircanada.com by October 10, 2008. Offer valid for travel until December 15, 2008 (travel completed). The discount will be displayed when you choose your flight.

This promotional code is available on one-way and round trip bookings only and does not apply on multi-city itineraries. In order to take advantage of this offer, you must make separate bookings.