Until 11:59 ET tonight, you can get some insanely cheap deals on JetBlue flights. The airline is holding its fall flash sale, which means you can fly around the country for potentially less money than you spent on your last outfit.New Yorkers already missing the summer weather can get to Orlando or Fort Lauderdale for $40. San Franciscans can party in Vegas for a mere $20. With the same amount of money, Bostonians can head south to New York or D.C.These ultra-cheap fares are only available on a select few dates, mostly in October, so you've got to be flexible. But if you've got a bit of vacation time saved up this year, this is one very inexpensive way to use it.If the timing's not right, though, don't worry. JetBlue has a sale like this every weeks . Just make up your mind, because seats this cheap will fill up quickly.