go and see the Amsterdam zoo, take a stroll along the canals (Grachten) and the shopping main street, and finally, take a look around the Redlight District
oh- and what about the Sex Museum? The entrance is just NLG 4.50 - you'll see some really pervert and S/M things, which would be strictly forbidden here. But believe me, it's interesting to see... :-)
Fondest memory: the tulips
Favorite thing: Another particolar zone is the Artis. Here you can visit the really beautiful garden and the acquarium...