This bag falls into the category of: “Why didn’t I think of that?” The Eclipse Nova Solar was made with the DSLR user in mind. It can charge AA and camera batteries by harnessing the power of the sun. I don’t think the cave photographers would get much use out of this, but it could be great for nature photographers. $150 from Eclipse—kind of ironic the name of the company is Eclipse, and they make solar gear.
Product Page [Via Gearlog]