An old refrigerator with the smoke fed into the bottom through stovepipe from a firebox about 12' away so the smoke can cool some and not roast the meat hanging in the frige. Pull out the sealing gaskets and the smoke can escape slowly.

go to smokering.com for some good designs

The best smoker/barbeque I ever saw was made from two 40 gallon gas water heaters. Parallel, over/under. 3" exhaust pipe connector at one end. A spacer and the final exhaust pipe at the other. Both cut for a swing-up lid. Angle-iron supports inside with heavy expanded steel inside for the grill in the top water heater. Fire/smoke only in the bottom. Grab your welding gear and go for it!

My dad built one out of an old refrigerator using a thermostat for a water heater to regulate the hotplate with pot of chips in the bottom. Worked great till we tried to smoke a big greaser lake trout. Opened the door to check and the grease was all over and exploded into flames. Dad was sure pee-ohed.

I have made a couple smokers by using 55 gal. drums. I cut out the top to put in my meat then cover it with a large kettle. At the bottom I cut a 12x12 inch square to load wood and put hinges on it so I can swing it open. I have access to several 55 gal drums so that's why I went with them.

Streack
I start by cleaning out the barrel thoroughly because my scrap barrels previously held oil. I cut out the top and the bottom. I have a large can opener type device I use to do this but anyway one could find to do it would be sufficient. Next I make the 12x12 inch or a similar sized opening in which you load wood. I also fix a grate just inside the top which I place the meat. I like to keep the grate as far away from the fire as possible so to be sure to smoke the meat instead of baking/grilling it. I have found kettles large enough to fit over 55 gal. drums at antique stores I have found them anywhere between $25-$100. If I can't find one cheap enough I cut a piece of scrap wood to fit over the top.

you could make a cold smoker for cheese and bacon