If you are just interested in camping at state parks in Florida, the reservation window opens 11 months in advance. So now, if you're looking to go this year, your best bet is cancellations. There are always cancellations, but you have to check for them pretty much daily. At a lot of the state parks in Florida, there are also some non-reservable sites. They don't really make this known, nor are they actually listed specifically. The strategy is to get a reservable site for a couple of nights, using a cancellation, and then extend your stay by moving to a non-reservable site when your reserved stay runs out.
-Speak