What can you tell me about camping cheap or free in Florida?

Lowest costs and free would be the local national forests. There free dispersed camping can be found and low cost developed sites. Some of the more developed sites get popular and pricey requiring reservations six months in advance. The "free" camping area's are usually undeveloped and or have few amenities, you may have to "hike" in or drive out to a wild lands area.

Another source of "free" camping are what is called "boon docking" generally these are like the above dispersed areas that offer few if any amenities so you must bring your own everything and as such are more popular with the RV crowd being fully self contained units.

So yahoo search your local national forest and look up "boon docking sites near you.

Here is the Yahoo "Boon docking" group with lots of info,

research campsites online. Compare and find the best deal. Prices tend to be cheaper in winter. You could wilderness camp. If you do this hide the reflective lights on your tent to reduce risk of being spotted. Get up early in the morning to reduce risk of being spotted also. Wilderness camping is illegal in some areas.

Which part? I do the FL. Keys cheap! Any National Forest in FL, is free.