usb device powered direct by AC
for EU: http://www.dealextreme.com/p/usb-power-adapter-charger-for-iphone-4-white-100-240v-eu-plug-48615

for us: http://www.dealextreme.com/p/usb-power-adapter-charger-for-ipod-series-iphone-3g-4-red-100-240v-us-plug-65369

for about 2.5 bucks free shipped you have a 110-240 Vac to 5Vdc 1Amp
while a regular USB port 0.5 amps delivers.