Fun things to do with prisoners:
You will need:
1. Cage traps
2. Holding cells
3. Method of transporting prisoners to a 16x16 square room
Catch your soon to be playmates in cage traps, and designate stockpiles in the holding cells for your prisoners, one cage per cell. You may perform experiments in the cells themselves or in the playroom. The cells are good for elemental experiments, like fire resistance/disease/starvation/creative killing, and the playroom is good for fighting prisoners, for training or for entertainment by making them fight a hopeless match. I keep my prisoners well fed for my weekly "fight day", where I have my prisoners, unarmed, face one armed dwarf. If a prisoner manages to kill a dwarf, I recapture him and starve him. All other prisoners become corpses crushed under a drawbridge. I might bring in a troll or two to kill some prisoners just for fun. Be sure to put a few corpses in locked prisoner cells with occupants and poor ventilation, the miasma is fun!