I've read you could buy a cheap plastic trash can, like one you'd use for a kitchen, to grow potatoes in. I've been thinking of growing potatoes in a container too but that's as far as I got in the research so far.
It's not much, but I hope that bit of info helps :)

If you go to the square foot garden forum there is an idea by Sinfonian that looks good. He makes a "build as you go potato bin". If I can I will post a link to his site. Follow #2 on the left of his site.

Here is a link that might be useful: Sinfonian site