Southwest.
We normally get the flight that is Seattle - Phoenix - Orlando. You don't change plans in Phoenix, you're just there long enough to unload passengers, switch seats if you want, and then load new passengers. About 20 minutes, so almost as good as a direct flight.
We have been lucky enough to get fares for $198.00 RT plus taxes ($99 each way).
We've flew with Southwest in Jan 05, April 07, April 07, Dec 07 for Christmas, and April 09.