Nice writeup on
how to build a smoker from a trash can. After seeing the Alton Brown episode refered, I seriously intended to do this when wild salmon was in season a month ago- but never got around to it.
Alton used a cardboard box which made construction easier and would take less space (just recycle the box when you're done), but obviously durability wouldn't be the same- and moisture rentention would be adversly affected. The garbage can would be the way to do if you have the space and interest.
Time to smoke me up some guinea pig.