Above Ground Pool Solar Panel Pool Heater 40 http://www.thepoolfactory.com/
This is how I made a really cheap solar pool heater, and it works! It is a simple coiled hose attached to a wood frame and placed on the hot concrete. The pump is for a pond and moves 900 gallons per hour. The hose is 3/4" and about 200 foot long. It will heat the water about 5 degrees above the ambient pool temperature on a partly cloudy day...
Solar panel made of pop cans
http://wanelo.com/p/3870902/make-solar-panel-wind-turbine-homemadepowerplant - Building a solar panel heater out of aluminum cans
Build It Solar, a renewable energy site for do-it-yourselfers, just free ideas, plans and information.