Between DCA, Dullas, and BWI, there are plenty of flights available. I've actually found that Kayak is nice just because I can compare the pricing for all 3 airports at once by just picking Washington as my departing city. Unfortunately, most individual airline sites require picking a single airport which can be annoying when the airline flys out of several of them.
Now... In May I got a non-stop RT on Delta from DCA to MCO for $189 (including taxes).
And I just paid about a month ago about $275 for a RT in November on Southwest from BWI to MCO (nonstop).
Since my May purchase however, I know flight prices have gone up across the board for most flights.