Sjokomelk (Chocolate Milk). None of the ones you can find here tastes as good as the one we have in Norway, and I've tested a lot :P
Brunost (Brown Cheese). I think this cheese is quite unique to Norway. Impossible to find here I think. Usually tell friends to bring back some when traveling to Beijing :)
Salmon and Smoked salmon. This you can find in most western markets, but usually to a very high price. Instead, I go to SanYuanLi Market and buy Smoked Salmon (1kg) for 90 rmb, Gravelax (1kg) for 140 rmb I think, and fresh Salmon for 40 rmb pr 500g (jin).
Crisp bread. You can get this at Jenny Lou's and April Gourmet. The types/brand varies from time to time.