Andrew Hyde, Boulder entrepreneur, has a mining cabin office. In fact, if you google "mining cabin", his comes up as the top entry. (I guess mining cabins are old enough that they're not on the internet much.)
His office is part of skinnycorp, the host for Blogcamp Boulder last weekend. If you're ever in Boulder, I'm sure they would welcome a visit. And you don't need to be skinny to enter.
Anyhow, I thought it was a very creative approach to office-ness. (How can you make your office space more interesting?)