If you have an American Express credit card through JetBlue, you're in luck. The airline has announced a new promotion allowing two people to fly for the price of one (also known as a "free" companion ticket) once you use your airline AmEx card.
I put "free" in quotes because of course nothing is really free, especially when you're talking about air travel. In this case the cost is actually airline taxes and fees. If you're wondering how a free ticket can be taxed, you're probably not alone—but suffice to say, it can be and it is.
There are also some airline-imposed restrictions around the free flight. You have to be a member of JetBlue's frequent flyer loyalty program (which really is free) and can only travel on the free ticket now through March 31, or from April 24 through May 23. Travel is valid on JetBlue's entire route network, which is a nice bonus.
If you don't have a JetBlue credit card, you can apply online.