has started selling a kit for a pretty sweet light-dependent oscillator (misnamed a theremin by most people). The thing that sets it apart from most similar designs is that it uses a solar cell, not a photocell, so it requires no battery. I like the idea of not having to power things at all, but it's hard to get solar cells that are cheap/small enough to power more complex circuits.
You can buy it here
for pretty cheap, with our without the altoids tin. Futurlec
has good prices on solar cells, but I haven't bought any, so I'm not sure how well they perform or what they are suited to power. If anyone knows the current draw of the MFOS
soundlab or WSG, maybe those could be powered by the 9V one. Any experiences using solar cells?