Spirit Airlines is offering airfare for as low as $9 each way (before taxes and other fees). I even came across a Fort Lauderdale-Freeport, Bahamas fare in December that was $2 (again before taxes and those pesky fees).
You must book "Individual travel-date specific fares" between November 21, 2008 and November 24, 2008. But all other fares can be booked between November 21, 2008 and November 24, 2008 for travel between November 28, 2008 and February 10, 2008.
For a full listing of all the fares and other terms and conditions, check out SpiritAir.com.