There is a whole thread on "iPod in the Fusion" on this board. I originally ordered a Peripheral PXDP-2, and installed it but it was unreliable, and was recalled by the manufacturer. I have just ordered a revised unit from discount car stereo. It should be here in a week or so, and I will install it.
I will surely post my experience as soon as I get it in. On the other thread, I mentioned some of the issues I ran into in the original installation, in several posts. But I'm willing to try again because the radio choices here in Connecticut suck, and I want to listem to my iPod when I drive.
There is another Peripheral product (PXDX-2 I think) which sternyy installed (see the other thread). He reports good results.