Solar panels are a popular item among people who are trying to do more with less but, at least in the past, they have been pretty expensive to install. For some uses, you can forget using solar panels and use the sunlight directly with very little efficiency loss. A device that lets you do that is called a heliostat, which is really just a fancy mirror that you can set to reflect sunlight to wherever you might want it. You could aim it through a window so that it hits your ceiling and diffuses throughout the room or you could point it towards a location where you could collect the sun's energy to heat something directly.
For a really good rundown on how heliostats work and how you can build one, check out this page where you can find all sorts of information. Heck, they even have an Arduino controlling some of them!
