SODIS method of creating drinking water. Everyone should know this.
Learn how to purify water with the sodis method. Even though I already knew you could purify the water this way, I did not know that even if you have boiled the water before storing, it can still be contaminated. Everyone should read and know this.
Here is a really in depth article about it. 1,000 Bottles of Water on the Roof, by James C.