One of the difficulties with solar panels is that each individual cell produces only a relatively small voltage and current, even provided it is placed in very direct sunlight. This means that large panels are necessary to generate enough energy to power homes. Additionally, since the power produced by panels is being produced during the day when no one is home, a battery system needs to be assembled to store and direct energy being used by the home. But as technology improves and consumer demand shifts toward longer battery life and better environment impacts, portable electronics have become the perfect application for solar technology. They already have batteries built in, they have sockets intended for charging, and they (preferably) use energy at a slow and steady rate. In other words, these devices spend a lot of time sitting around; time during which they could be recharged by the sun.
Voltaic Systems is a young company that has gain notoriety for manufacturing backpacks, bags, and laptop cases with small solar panels built in. The panels are tough, lightweight, and waterproof and use high-efficiency mono-cristalline cells designed for maximum current (which means the faster charging times).
Voltaic Systems currently produces 4 bags: The Backpack, Converter and Messenger produce 4 Watts, which is the means that One hour in the sun generates 3 hours of iPod play or a 1.5 hour cell phone conversation. Plus the energy is absolutely pollution free. Their 4th bag, the Generator, produces 15 Watts and is the first solar bag powerful enough to charge a laptop. The Generator has a built is battery allowing it to store energy and to achieve voltages high enough to charge more demanding devices.
For an eco-techie on the go, these bags are an amazing achievement.