Here's a quick update on the cheap solar water distillation project. Yesterday, I tried adding a simple reflector made of aluminum foil taped over cardboard. Unfortunately, the weather didn't cooperate: solid overcast all day. As a result, the control still without the reflector produced no water, making a comparison impossible. The one with the reflector may have produced water, or I might have spilled some into it -- I'm not sure. I'll rerun the experiment once we get some sunshine on a weekend. (I have to be home all day to periodically re-point the reflector at the sun, which is one drawback of using a simple reflector. A cylindrical reflector would be better about tracking the sun, but it'd also be harder to make.)
Also, a neighbor turned me on to ceramic filters being made by Potters for Peace, which seem to be a beautiful example of high-tech theory producing a simple, effective, low-tech design. I'd love to get my hands on one of them to check it out.