I've been searching for quite awhile about How to?...ending in...iPod and I've come up with a couple of links that were very helpful.
Here's the first:
http://www.installer.com/ipod/
Installer dot com has a lot of useful cables and the like. (ie how to hardwire, charge and play at the same time)

Second:
http://home.swipnet.se/ridax/connector.htm
Ridax can supply breakout boards and the like for iPods.

Last:
http://pinouts.ru/Devices/ipod_pinout.shtml
Handbook of hardware pinouts, cables schemes and connectors layouts.

These sites helped a so much I thought I would pass the info along.
Also I must give accolades to Car Audio for Dummies by techtv/car electronics expert Doug Newcomb