If you are not real picky on your dates...
If you are not real picky on your dates try
www.cheapflights.com. I have found fairs from DC to Pop as low as 250 US and from NY to Pop as low as 120 US. It is random but have never seen them any higher than 450 US for either. Then again they select the dates... so you either travel on those dates or you do not.
Hubby and Best Friend has come several times this year and the cheapest ticket we have gotten off of aa.com from Wash DC to Pop is $452 US and the maximum we spent is $660. I guess it all really depends on when you are flying. I tend to find the best fares at like 6am...then when I search again at 9am they have all jumped up a hundred bucks or so.
Another thing I have been doing lately is a combination of travelzoo and aa netsaver specials. If you do not mind traveling on a weekday, netsaaver normally always has either MIA to POP or MIA to STI from $99 - $169 round trip the week before the trip and travelzoo.com has been offering r/t tickets from Washington, Newark or New York to Miami for $99 r/t or less normally every week.
GG