The two-week sale features a whole boatload of deeply discounted one-way fares across the country, though there are quite a few particularly tempting offers up for grabs from nearly every airport Southwest serves. You can peep them all, and sort by departure city, on the airline's flash sale site. The only catch is that you'll need to book your trip before 11:59pm on April 19.
The standout domestic deals at the moment include $81 flights from New York to Chicago (and vice versa), $49 flights from LA to San Francisco (and vice versa), $99 flights from Chicago to Charleston, and $56 flights from Portland to San Francisco (and vice versa).
As for international options, there are wildly affordable $59 flights from Ft. Lauderdale to the Cayman Islands, Belize, and Turks and Caicos, $98 flights from Houston to Mexico City, and $99 flights from Tampa to Cuba.