USB Solar Charging 4-Port Hub with Torch
Just to be clear, that's "with torch" as in the British word for flashlight. Now that we've established that there are no flames involved, we can point out that this hub ($22) from Brando has a built-in battery that can be charged with sunlight or via a USB cable to your computer.
In addition to providing four much-needed USB ports for your peripherals and other devices, it can also use its internal battery to recharge your phone or MP3 player in an emergency -- it comes with seven adapters for common mobile devices. Just throw this in your backpack for when you need extra ports or power (or a flashlight) in a pinch.