I've been doing a lot of research on DIY solar panels that use alternative materials that are a fraction of the price of factory made. The links below offer some great info for all the different styles/versions of DIY designs. Great for the shop or home. Aside from cans folks are using aluminum gutters, metal soffit, roofing and door screen instead. I am building my prototype over the next month - with soffit - and will keep you posted on the design!!
http://www.builditsolar.com/Experimental/PopCanVsScreen/PopCanVsScreen.htm
http://stonehavenlife.com/7-diy-pop-can-solar-heaters/
A solar hot air collector made from aluminum soffit that is normally used in construction. This panel can be mounted on your home, and reduce your heating bills substantially. And it's maintenance free!