I'm a namby pamby computer programmer and I managed to build one.
I used this video as the basis...
[ame="http://www.youtube.com/watch?v=JiBy2eR6a6E"]How to Build a Verticle Drum Smoker. UDS 55 Gallon Drum Smoker - YouTube[/ame]
For a novice, the tricky part will be the large holes at the bottom and the charcoal basket.
If you buy a stepped drill bit, the large holes will be easy to drill. As for the charcoal basket, I'm using an old washing machine drum so no welding/construction needed.