It's hot out here, and this since two weeks. Temperatures rise daily above 30 degrees Celsius, and that's exceptionally hot. Geoff Milburn decided to put his thermodynamics classes to work however, and produced this ~24$ homebrew air conditioner. It'll cool a room to a comfortable level in 15-20 mins, and will run for a few hours on a garbage pail full of water. It's cheap, environmentally friendly (just fire the waste water off to your garden), and makes a good one hour project for a quiet evening.