I've dreamed about having suntube skylight like those from SunTek or other manufacturers ever since I first saw one. While this DIY suntube won't replace those from traditional manufacturers, it would work well in a shed or unpowered cabin.
Unfortunately, there aren't any still photos from this video that showing how surprisingly well the soda bottle light works. I've posted a few screen captures below but the main idea is that the soda bottle, filled with water and mounted in a hole in the ceiling, collects light from the sun and distributes enough into your space to supply adequate light for your daytime needs.
See a detailed video here on Youtube.