I bought this portable solar panel from SolarStyle on eBay for $20. This small solar charger has a built in battery (see this previous article for more information). With this portable solar panel, I charge my MP3 player, a portable amplifier, a set of battery-powered Sony surround sound speakers, a cellular phone, a digital camera, two LED lamps, a LED booklight, and a LED flashlight. If you are already positioning yourself to optimize sunlight, it is quite simple to do this. If I added a $50 solar panel, I can power two laptop computer, and have all of my audio-visual and computer devices running on renewable energy.