I'm starting to play with basic functions of an iPod and iPhone
There 30 pins total on the standard iPod connection.
Here are the important ones for basic manipulation of music:

1, 11, 15 - Ground
3 - Right audio out
4 - Left audio out
5 - Right audio in
6 - Left audio in
12 - Tx (transmit over serial)
13 - Rx (read over serial)
18 - 3.3V Power
23 - 5V Power

V = iR is basic Ohm's law. Love you EE220 at Purdue. Damn I struggled in that course..
Arduino provides 5V from the USB, standard.
Arduino outputs at 0.5 amps.
iPod charges at 5V, maximum 1 amp so no resistors are needed.

Hooked up all grounds and 5V from the arduino - iPod is charging.
Hooked up Tx on iPod (pin 12) to Rx on Arduino (digital pin 0), and Rx on iPod (pin 13) to Tx on Arduino (digital pin 1).

Contact me at tullrich at gmail.com for the arduino code.
here are the references I used to piece together code.

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