Small Scale Hydro- Here are some good references for planning, designing, and building a micro-hydro system. Step zero is to carefully determine if you have a hydro resource that is worth developing -- some of the references cover how to do this in detail.
Cool idea: Tutorial: DIY RAIN CHAIN from Wire-Wrapped Rock. Rain chains are a beautiful and functional alternative to traditional, closed gutter downspouts. Guiding rain water visibly down chains or cups from the roof to the ground, rain chains transform a plain gutter downspout into a pleasing water feature. From the soft tinkling of individual droplets to the soothing rush of white water, they are a treat to listen to. They are widely used in Japan.
Micro hydro power generation system for building roof rain water flow to power ac&dc loads.AVI - http://www.newvistaenergy.com/hydroelectric-energy/hydroelectric-energy-facts/micro-hydro-power-generation-system-for-building-roof-rain-water-flow-to-power-acdc-loads-avi/