Most of what I do is already powered by renewable and sustainable resources. I even had my computer and lights hooked up to an 80 watt solar panel for a while (but housing problems and marital problems led to my solar panel, my controller, and me all being in different places at the moment, so that's not an option right now, but in the future solar will definitely be my main power source for the couple of electric-powered things I use).
But for this mission, I was able to find one simple, yet useful solution to my lighting needs during the daytime. Normally I'd choose to do my work sitting in a room with lots of windows and facing south. But where I am staying now, that's not an option, and I have to work in a room that is quite dark even in the daytime. So I usually turn on the light. Now, the bulb is compact florescent, of course, but still it is using up energy that the planet can't really spare. Plus, I just hate having to use lights in the daytime!
So, I let a little brainstorming happen in my head, and came up with all sorts of ideas for making homemade, recycled versions of those solar tube "skylight" things that work like a tunnel for sunlight, as well as some ideas for using a bunch of mirrors like in a periscope. And I may still try something as complex as that. But for now, so that I wouldn't have to go another day wasting non-renewable energy on my lighting needs, I stuck a large piece of reflective bubble wrap that I found in the trash on my ceiling, aiming the reflected light at my laptop. It's not a miracle or anything, but it's enough brighter that I can work without the electric light, which is a small, but notable improvement. The rest of my room is dark as hell, but my little spot by the window is not so bad, even on this cloudy, rainy day... :-)