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:
Installer dot com has a lot of useful cables and the like. (ie how to hardwire, charge and play at the same time)

Ridax can supply breakout boards and the like for iPods.

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