There are some great deals going on to the Caribbean from the East Coast for only $50 each way on JetBlue. The departure cities include Boston and New York.
There’s also some domestic flights available for $15.
I subscribe to the Flight Deals tweets and check them pretty often. I may have booked deals during work meetings. (If my boss is reading this, disregard the last sentence).
I can jump on fares when there’s still lots of availability and I don’t miss out on the deals I want to take advantage of.
I’ve shared my process of “subscribing” to great fares.
This process involves signing up for twitter. Even if you won’t be an active user of twitter, it’s a good idea to have an account to take advantage of deals on contests in general.
I recommend following them even if you aren’t in those areas because they are gateway cities. There’s a lot of good international deals–worth the effort flying out to the gateway.