Check out the Voltaic Backpack
Since writing an article about the orignal Voltaic backpacks way back in 2005, the company continued to innovate in the backpack-as-charging solution space. There are now several options and some include enough power to support laptops in addition to all your other gear. These are definitely an interesting solution if you spend hours away from available charging power or have a commute that involves walking outdoors.
Here’s what I originally said about Voltaic in March 2005: I’m not certain anything solar powered is a great idea in mostly cloudy Seattle, but for many other parts of the world, using the Voltaic Backpack to generate backup power as you cruise through your day on foot makes walking seem more attractive. With more exercise and the assurance you’ll never run out of juice while waiting for a delayed flight this is sure to be an excellent replacement for your current backpack. Solar panels generate up to four watts of power and the battery pack inside stores 2200mAh of reserve power, which is enough to give your cell phone, iPod, Pocket PC, digital camera or GPS some extra juice at a critical moment. Two versions of the bag covert stored power to 5V, 6V and 7.2V or 3.7V, 5V and 6V respectively. This still won’t solve issues with a laptop that burns through juice but the rest of your digital world will stay online. Be sure to consult your product manuals to determine which voltage is required to make sure you don’t fry the internals. Beyond providing extra power, the Voltaic Backpack also includes a useful assortment of pockets to keep gadgets neatly organized and cables under control.