Stanford University researchers have announced that they can turn ordinary paper into a battery simply by adding special ink and drying it in an oven. Not only is this WAY cool but it has enormous practical applications -- assuming it can be developed as a low cost, low weight alternative to ordinary batteries.
The special ink contains carbon nanotubes and the paper provides a substrate on which the tubes can link up. One caveat is the apparent use of lithium solutions and electrolytes as a second step. Lithium is still a potentially limited resource -- unlike carbon and paper.