iFixit tore apart the 3G iPod nano and the iPod classic, and in addition to finding the usual array of LCDs and hard drives, they discovered that the screens are now backed by a metal plate. One can only assume this is to make the screens less prone to breaking, and considering how crack-happy earlier iPod models have been at times, this is a welcome addition.
In addition to the metal plate, the deconstruction revealed the nano has approximately the same surface area as the previous nanos, and there is an increased use of adhesive in assembling the iPods. The adhesive is only worth noting because it could make replacing your own battery a more daunting task. See the entire gallery over at iFixit. [iFixit via Apple Insider]