For those of you looking to pick up your Mercedes-Benz or Porsche from the factory, or if you're simply in Stuttgart for a few days visiting the... mistress, may we suggest you check out the V8 Hotel. Found in the Meilenwerk, "a forum promoting driving culture", the hotel is just a car-themed venue to be enjoyed by the whole family.
The hotel features a few different areas, including an old airport building that houses the standard rooms and something called "the old shipyard" that features the automotive rooms. Some of the auto stuff is pretty snazzy (like the Vision room), and some is delightfully tacky (the drive-in).