This completely sustainable treehouse hostel is pretty amazing. If you are worried about your ecological footprint, or just want to get away from it all, there's no electricity and very few amenities.
However, when does a vacation stop being a vacation and start becoming work? Also, with the amount of pollution created actually getting to your destination, do you think that it cancels out the savings when you are actually visiting such "sustainable" places?
The Hostel in the Forest sits on 120 acres of forest and wetlands, and features 8 tree house/huts with fun names like “dragon’s lair” and “peacock”. A couple of the huts have no power, but instead use candles for nightlight.
There are outdoor showers, where guests are asked to use only the provided Dr. Bronner’s Organic Soap. The compost toilets are modeled after the sawdust method designed by Joseph Jenkins in the Humanure Handbook which is available online for free.
http://www.ecospace.cc/travel/tree-house-hostel-1207.htm