Rain Drops, devised by Evan Gant for product innovation firm Altitude Inc, is a system designed for collecting rain water from the roof by simply modifiying the existing gutter system to store water in standard plastic bottles. You can use the collected water to water your garden or wash your hands.
A further benefit to using plastic bottles as a water collection system is that it makes use of a process called SODIS, which uses a combination of the suns UV rays and heat to remove pathogenic microorganisms that cause disease.