Do you happen to live near an Ocean State Job Lot?
I just picked up an RCA to iPod dock "slot" cable connector made by Mad Katz (the company who makes ipod, PSP, Gamecube, X-box, ect. accessories)- one end has RCA connections, the other the connection that fits into the bottom slot of the iPod, the slot used to connect into a dock if you have one, or where you'd connect the ipod to a wall plug to recharge the unit, or to your usb/firewire slot to your computer.
I've never seen this approach before. Bought it, along with an iPod case, and car charger, for $9 on closeout- made to fit my 4th generation iPod.
Usually, I use an RCA to minijack setup, and I plug the minijack into the iPod dock I have for my 4th generation ipod.
What model is yours? The iPod video and nano models do well with connecting to the headphone jack, while the earlier models are better off connected through the ipod dock for fidelity, or through this neat device, the Sendstation Pocketdock.
USB version-
http://www.sendstation.com/us/products/pocketdock/lineout-usb.html
Firewire version-
http://www.sendstation.com/us/products/pocketdock/lineout-fw.html