Can I charge an iPhone with another device's USB charger?
Solution 1:
Yes, it works great. The iPhone charges over USB like many other devices. The iPhone can accept more current than the USB specification, so you might have a slower charge than a charger that provides that extra wattage, but the iPhone circuitry is designed to take any normal USB charge and properly handle the charge which includes pausing it when the battery is full.
Solution 2:
Also, just so you know, because I was curious about this myself, it is safe to charge the iPhone/iPod with the larger 10W iPad AC wall charger. http://support.apple.com/kb/HT4327