There are a few notable issues with generic USB chargers. The computer needs to be on to charge, you need different chargers for various devices and you may need software on the computer to start charging.
With the CSQUID, there is CHARGE mode to allow you to charge even when the PC is in standby [...]

The Pico by Freeloader is a portable solar powered charger designed to charge mobile phones, iPods, GPS systems, and most other portable electronic devices. The Pico has advanced solar panel and battery technology to help provide a quick charging time for the devices internal battery and a quick time for it to deliver the power [...]

The very first Apple-certified iPod chargers will available very soon from the company Novothink. Their Surge charger is a hard case compatible with the latest generation of iPod and iPod Touch. A version for the iPhone 3G and 3GS will be available by the end of the year.
The case is fitted with solar [...]

Tremont Electric has created a kinetic energy-based charger called the nPower PEG, otherwise known as a Personal Energy Generator. The PEG can charge a portable device up to 80% with an hour’s worth of movement. You don’t need to attach the PEG to yourself to gather the kinetic energy. It can be placed in your [...]