Step 1: Parts
Radioshack 7805 5v Regulator
Radioshack 7812 12v Regulator
2 x 1k resistors
2 x LEDs
USB female socket
Firewire female socket
Step 2: Breadboard it.
But where you need to pay attention, the 5v regulator powers the USB.
The 12v regulator powers the firewire.
Do not mess that up, or you'll blow up the ishuffle.
One more time, don't forget 12v=firewire 5v=usb.
So if you are looking at the USB connector, pin 1 is positive and pin 4 is negative which in WWIV BBS ascii art looks like:
+ | | - .
On the Firewire cable If you are looking at it with the pointy part down, pin 1 is positive and the pin across from it, pin 2 is negative in bad ascii art it looks like this:
Step 3: Hook it up
There are a lot of ways to power this, I put on a dc jack, so I could use an old wall wart or plug in in to my car to charge. Do what you want... Another slick idea would be to use a firewire plug and use the apple ipod charger wall wart to power it.
I also put one of these inside the simple ipod amp project I did, so I can charge the ipod while listening to musc.