Intravee mate
If you have nav it's additional features are great too.
This is what I use and many many others.
Otherwise Denison.
A quick search on the forum about this will bring up several results
To use one you have to buy the intravee from toysinyourcar and then source an Alpine KCA-420i for your iPod to connect into.
this replaces the CD changer which if you do want to keep you need an additional alpine module.