If you want a simple quadband unlocked phone, I can recommend the Blu T200. It's small and power efficient. I bought one for $35 on Amazon, but it can sometimes be seen for around $25 on ebay. There is also a T210 version with two SIM slots.

The included power supply supports 100-240V 50/60Hz. The phone connects to the charger through its mini USB port. It can be charged from a computer USB port with the proper cable.