Book HERE through August 1st for travel between August 23rd and December 14, 2011. Blackout dates apply, including Fridays and Sundays. Not all routes are included. One example of a $59 fare ... Chicago, Midway to Nashville.
Southwest Airlines discounts a selection of 1-way fares starting at $29 as part of its latest sale. (It advertises prices starting at $59, but several flights go for less.) Flights must be booked by August 2 at 3 am ET for travel from August 23 through December 14.