So much to do in so little time!! Walk the Stroget, eat smorresbrod at Tord and Snaps at Nyhavn, see the lights in Tivoli. As an embarkation port you couldn't ask for more then Copenhagen. There's a wealth of sites in the city and tours to Hamlet's castle an hour away. Take an extra day to wander. Hotels are small and pricey with no AC so stick to the American ones if your not adaptable.
Taxi to the top of the hill and walk your way down though the streets of Tallinn. The medieval fort and the stone walls belong in a story book. Save your money to buy one of the fantastic hand made sweaters sold along the city wall. Eat in the town square and take lots of pictures.
There's no time to explore this port if you're heading to Berlin. Book your tour in advance with SPB tours and you can get discounts for multiple tours. Berlin was incredible but remember that everything you see is a restoration due to WW2 damage. The story of the Berlin wall was worth the trip.
Overwhelming port. The palaces, parks, fountains, churches are too beautiful to describe. Again SPB tours did an excellent job of telling the Russian story. It's exhausting but if you've got the energy take the evening vodka cruise tour in addition to the 2 day tour.
Grab a hop on/off water bus and you can see most of the old town. Hop off to see the Vasa Museum and then ride to the top of old town and walk down to the palace. Stop off to eat in the square in front of the Nobel museum. There plenty of shops to find inexpensive souvenirs.