US DOE-Solar Water Heating

http://energy.gov/energysaver/articles/solar-water-heaters

The U.S. Department of Energy has developed a site specifically focused on solar water heating. This site provides an overview of the technology and the opportunities to save money and energy. There are links to find equipment, evaluate your site, determine the proper system size, etc. There are also links for other water heating options such as tank-less hot water heaters, heat pump water heaters, and others.