Porter Airlines has yet another promo code offer, this one for summer travel. Just enter code BEACH12 at time of purchase on flyporter.com. This offer is valid for travel through September 4. Book your seats by midnight, July 20.
And Air Canada has a summer promo code of their own: Save 50% on travel to/from the US and Canada through December 14 with promo code USPROMO17JUL12. Book by midnight, July 20.