In my next fortress, I am going to build a wide trench around my starting location. No big surprise. There will be a retracting bridge over this wide location. Again, no big surprise.
All immigrants without desirable skills (and eventually, when I have about 25-30 good dwarves in my fort, all immigrants period) will be chucked into the trench via the retracting bridge.
Inside the trench I will ensure they have a few units of stone, and some surface-growable seeds [rat weed and prickle berry most likely]. I'll build a few farm plots, a few breweries, and turn on everyone's farmer and brewer skills. And then I will leave them to their own devices. Anything that falls into the trench is fair game for them, so they ought to have a fair number of bolts and severed goblin limbs after a while.
If I feel particularly kind I might also designate my garbage dump to be over the side of the bridge. It seems fair. Thus they can have anything they can construct from refuse, except they are not allowed to build their way out of the moat.
What? We sent a missive to the mountainhomes informing the emmigration office that we would be accepting no more migrants!! All things considered it's rather humane!
[ May 26, 2008: Message edited by: Erk ]