We'll suspend our general disbelief for a moment to talk about the Renu, an unbelievable but incredible solar product that's actually coming to market next year.
The ReNu probably doesn't work as you'd imagine from looking at the photograph. Sure, you see an iPod dock with speakers, just as you'd expect. But that huge back plate is actually a solar panel/battery combo that you can remove from the dock to hang near a window to store energy. It takes about 9 hours to charge in direct sunlight, or 20 hours to charge in indirect sunlight, to power music for 7-8 hours.
This ReNu panel actually supports a variety of different base units, including a pure iPod/iPhone dock (no speakers included) and an LED desk lamp.
I think the basic idea becomes something like, hang or place a bunch of solar panels in sunlight, then grab power as necessary. But in case you find this ease of use scenario as hard to believe as us, all of the docks and the ReNu panel itself will plug in should the sun's juice fall short.