Southwest Airlines is celebrating their 40 years of service with discounted fares. Fares are based on distance between city pairs (0-450 miles = $40; 451-1250 miles = $80; 1251 + = $120). Fares must be booked online at www.southwest.com by June 23rd and are for travel between August 23-November 16, 2011.
I was able to grab an $80 fare from Newark to New Orleans during this time period. Discounted fare were available almost every day (aside from Friday and Sundays which are excluded from the sale), but not for every flight option. These fares are available on a limited basis, so I would suggest booking quickly. And remember, with Southwest if you need to cancel a reservation, you will receive the entire amount paid back as a travel fund which can be used one year from purchase.