I had a harbor freight one that i put on a half ton years ago. It had a hand crank deal, which i replaced with a small ATV winch. I had to tie it into the frame, but for what it was it worked pretty well. At the time i was cutting firewood frequently, and i would be able to go and load the truck up in about 10 min or so, without actually lifting too much. You have to watch the swing of it because it just pivoted on it's own, but sure beat anything else i had at the time. I'll put some pics up tomorrow of what's left of it, i retired the truck a few years ago with the plans of pulling some parts. It would easily pick up a few hundred pounds on each pic, if you wanted, a better fabricated one would be nice. The one i had mounted in the bed, i would have to do some calculations and think on the stability of a hitch mounted one like the one pictured.
EDIT:
We have talked about this earlier but i think it needs to be said again; there is more than one way to skin a cat. If you have certain types of machinery that you use that work awesome in your application, that's cool. But that doesn't mean that owning that machinery is the only viable way to do work. In other words, a mini is awesome and can do a bunch of work, but low tech and cheap lifting gear also works just fine. While a mini is definitely better in several situations, a cheap truck mounted crane can move a bunch of wood in a hurry, without breaking a sweat, or needing to take another trip to get it. I used that cheap crane i had to load a 600 pound welder in the back of a truck all the time, and i loved it, and could load and haul a years worth of firewood in a weekend. It cost a couple hundred bucks, and nothing in maintenance. It needs a new solenoid switch for the winch, but i could hand a chain fall on it right now and lift stuff.