The Watercone is the most effective invention that I have seen to get clean drinking water. Amazingly simple, portable and brilliant. The only problem now is cost, but I believe they are working to get these mass produced, so they will be more cost effective to provide to the villages that need them the most.

I just bought the book Design Like You Give a Damn: Architectural Response to Humanitarian Crises. The Watercone is described on page 285.