Southwest Airlines Rapid Rewards members can show their card at the gate and get 20% off the price of 1-day tickets. It costs nothing to join and it's the best discount that I've seen that is available to the general public.
I don't think that they have a AAA "show your card" discount but you can purchase your passes ahead of time at your local office. I've found that the discount thru my AAA is not as good as the SWA RR one.