I really like that web site
BuildItSolar: Solar energy projects for Do It Yourselfers to save money and reduce pollution. It's what got me started on the hot air panel I have been collecting materials for. I was thinking of eventually trying a version of that hot water design. Since copper prices have dropped, it might be the material of choice. It would be neat to somehow tie it into the unused zone of my boiler to distribute the heat thru the house.