I came across a page about peak-power tracking in solar PV applications. I decided I wanted to goof around with solar stuff, so I started tinkering. This is what I have so far:

Solar Thingie thumbnail, click for larger version

So far there's not much going on. It measures voltage generated by the panel, and current being delivered to the load (a little red LED in this picture; the circuit is powered from a bench supply). I started adding a 5-volt LDO, which I'll use to regulate power to the MCU and LCD when powered from the panel.
If I can get AVaRICE to stop hosing my ATmega324P parts, I'll slow this down to 4 MHz (it's running at 16 MHz here) and power it from 3.3 V. That should work better in actual sun-powered applications.