I use this kit
http://us.kensington.com/html/14492.html
in my cab. I set up the remote control for my iPhone on the parking brake, rather than on the steering wheel as suggested for two reasons. I have the sport steering wheel so it barely fit, and I thought was a little intrusive there.
I also have Bluetooth so the phone fully integrates this way. No USB required... so what I do is use the Genius function in iTunes to build a few lists of 100 songs each in a theme and start it playing when I get in the car.
Mind you, I also have the satellite radio which accomplishes many of the same desires. But this is the niftiest connection kit I've seen!