This looks like a pretty good one. As part of a promotion celebrating Southwest's 40th anniversary, the carrier is offering $40 fares for flights from 0-450 miles; $80 for flights of 451-1,250 miles; and $120 for 1,251 and beyond. You must purchase before June 24 for travel from Aug. 23-Nov. 16. Blackout dates are Sept. 1, Sept. 5 and 6, and Oct. 10, and sale fares are not available Fridays and Sundays. Here's the fine print.
And some sample, one-way fares from Boston:
For as low as $40: Baltimore, Buffalo, Long Island, Newark, and Philadelphia
For as low as $80: Birmingham, Charleston, S.C., Cleveland, Columbus, Ohio, Ft. Lauderdale, Greenville/Spartanburg, S.C., Indianapolis, Jacksonville, Fla., Louisville, Milwaukee, Minneapolis/St. Paul, Nashville, Norfolk, Va., Panama City Beach, Fla., Pittsburgh, Raleigh/Durham, St. Louis, Tampa Bay, and West Palm Beach.
For as low as $120: Denver, Houston, Jackson, Miss., Little Rock, New Orleans, Phoenix, and Omaha.