BookArmor (tm) High Impact Travel Case for Barnes & Noble Nook / B&N Nook Reader
The case is built so strongly that I am 100% confident my Nook is fully protected during transit.  The case is a bit heavy, but I suppose that is to be expected of this type of product.  My only real complaint is that the price is a bit high.  At this point one has little choice in quality Nook cases, so you're stuck in this price range until there is more competition in the Nook accessories market.