I found this on another Forum and thought it may be of interest to some of you "techies":-
"HAND MADE" USB-CHARGE for NOKIA
This simple project shows you how to make a USB powered Nokia cell phone charger. The advantage is that it weighs much less than the bulky AC adaptor, and can be used wherever you have a computer or a laptop.
Step one: strip off the shielding and insulation on an inch or so of the usb cable. Clip the white and green cables to uneven lengths so they can�t conduct into each other or either of the power lines. Hopefully you should be left with a black wire and a red wire.
Step two: Clip off a length of the nokia chargers phone-side plug. You won�t be needing the wall wart part anymore. Strip off the insulation from the nokia plug wire. Hopefully you should have a red wire and a black one. the red wire should be connected to the inner barrel of the plug, and the black one should be connected to the outer barrel.
Step three: Attach a normal silicon diode (not a zener diode) with the line part towards the nokia plug. It should go between the red wires from both cables (see image). Attach the black wires from each cable together.
I suggest staggering the lengths of the wires so that the solder joints have less chance of coming into contact.
Check all the wires with a multimeter to make sure they are really the right ones! The colors might not be standard...