Check out Southwest’s . One way fares are $30 if you travel up to 400 miles, $60 for up to 750 miles and $90 for more than 750 miles. Fares are only this low for 48 hours – and many of the best flights are going quick!
Caveats: you must purchase the tickets on southwest.com or swabiz.com. Sale ends July 8, 2009, 11:59 p.m. P.S.T. You must travel September 9 through November 18, 2009. Travel valid every day except Fridays & Sundays.