We pulled into Ijmuiden (SP?) approx 1 hour away from Amsterdam. Having visited Amsterdam several times previously we did not get off the ship, but understand that Harlem is well worth a visit as an alternative and is only 30 minutes away (6 euros on the local bus).
Stunning panoramic views which took my breath away. Do your own excursion on the Flaam Railway to Merdel (sp?). The station is 5 minutes walk from the ship. Get off as early as you can and book your train tickets for late morning. Get back on the ship for breakfast and off again for your train! It gets busy late morning and people couldn't get on if they hadn't already bought tickets. 1 hour each way on the train and the views are lovely.
A few shops, a museum and boat tours available also.
Not the prettiest of ports (or opera houses!) until you go into the centre - a 5 minute walk away OR get on the hop on hop off bus outside the port. Coffee will cost approx Â(EURO)5 for a latte - be prepared!!