Solar Toothbrush

http://greenopolis.com/goblog/litegreen/solar-toothbrush-no-water-or-toothpaste-required

Just another way to cut down on water use.

Light-Transmitting Concrete

http://www.cement.org/decorative/translucent.asp

Definitely an idea for interior walls.

Save Water Bricks

http://dornob.com/old-red-goes-green-recycled-wall-brick-built-to-save-water/

Off the top of my head, I'm not sure what I'd use these for. But they're cool, and I'm sure I can think of something.