If you need an iPod or iPhone USB Power Adapter, you can spend $30 on another Apple USB Power Adapter. Or, if you're interested in giving your hard-earned cash to a company other than Apple, you can consider Griffin's PowerBlock.
The PowerBlock is your basic power adapter that comes with a USB dock-connector cable (like the one included with your iPod). An LED indicator shines amber while your device charges, and turns green when charging is done. The PowerBlock measures 1.25-by-2.63-by-1.13 inches; you can flip it upside-down and plug it into a top wall outlet, leaving the bottom outlet unblocked.
The PowerBlock's prongs can fold away when not in use, a nice touch. One very good reason why you might opt for the Apple adapter instead of Griffin's: The PowerBlock lacks the removable prongs that the Apple adapter has for Apples World Travel Adapter Kit ($40) or, if you have a MacBook, the power extension cord that comes with the laptop.
If you're not a world traveler and just need a power adapter for home or work, the PowerBlock does the job adequately. Though at this price, there's no compelling reason why you should opt for the PowerBlock over Apple's adapter--or an adapter that offers more value for your money, such as PDO's PowerTwo.