The stepfather and I built one last year.
We got an old stove from one of those used appliance places that still worked, but was in such rough shape they gave it to us for free.
We took one of the burners from the rangetop and put it underneath the fridge where the compressor used to be. We cut a hole in the bottom of the main section right above where we mounted that burner, and used the dial from the stove to control that burner, and made a door to acces that section. That way, the smoke burner was seperate from the heat burner, and we don't have to open the main door to add wood chips.
We mounted one of the oven elements on the floor of the main smoker section to control the temperature. We reverse engineered the oven control to make it work, but I wouldn't reccomend that. It is just not sensitive enough.
The one problem with using an old stove is that you would need 220 available to run it.
I have heard good things about a controller from Mcmaster-Carr. Model number A319. The part number is 1760K71. I haven't researched them myself, but it supposedly goes for around $55.
[This post was last edited on 12/26/06 at 10:51 PM]