I've installed mine behind my head using some massive double-sided padded tape. Even with autocrosses, it does not move.My recommendation would be to install it like warrenw did behind the seats. There is a place there to plug it in behind the driver's head. Mount the adapter in the center along the "spine" of the center speaker hump somewhere, then cut two small holes, one in the back of the center console (hidden from sight) and the other directly behind that one in the center speaker hump (also hidden from sight) to run the iPod cable into the center console. Get the right rubber grommets and choose your hole size carefully, and you will have an invisible installation, yet have easy access to the iPod, plus adjustable cable length. It is real easy - remove the horizontal panel behind the driver's head for access - pretty much a screwdriver and drill job. You could do this job easily in one hour.
Warrenw has the best installation I have seen, including my own.
I found that you do not have to drill the second hole in the center speaker hump- only the one in the center console. There's enough room to route the cable behind the center speaker trim on the driver's side to come out right behind the center console. You do lose a bit of the ability to move the cable in and out (mine moves about 6" total), as you need to coil the cable between the center console and trim to give that ability, and there's not much room there.