I like the Princess cryise line that leaves from Copenhagen.

Try to get a cruise that has Oslo and/or Gdansk also.

Our favorite cruiseline is Oceania--for the small ships, outstanding service, port intensive itineraries, excellent food, lack of formal nights, open seating dining, no charge specialty restaurants, Tourist Office reps that get on at every port.

Because DH has a tendency towards motion sickness, we book a cabin as low and midships as possible. We love a balcony, but have enjoyed cruises in an inside cabin as well.

We like to tour the ports on our own, rather than take the ship's shore excursion. The exception to that is St Petersburg, where we had a wonderful two days with a guide & driver from Red October.

At www.cruisecritic.com, you can get lots of additional information about ports and ships.

The link below is a trip report posted here at Fodors cruise forum on a Princess Baltic Cruise. Hope you may find the information useful or interesting.

http://www.fodors.com/community/cruises/baltic-cruise-in-june.cfm

Private tour is cheaper and you get to see more (not that much cheaper, maybve 15 to 20% compare to ship's excursions). You must be careful on who you select. Check here for "referecnes".

We took 4 private tours and 2 Princess organized tours on the Baltic trip. We decided on the Princess tours for "safety" reasons more than anything else.

Ship's excursion will guarantee to get you back on board even if the group missed the boat for whatever reason. With private excursions, if you miss the boat, you are on your own.

Looking back, there are some ports that you are better off not booking anything (not even private tour) and just do your own exploration. Tallinn, Helsinki and Stockholm are quite easy to navigate on your own. Many main attratcions are walking distance or just a short bus ride or a cab ride from the dock. Locals speak some English and cabs are usually plentiful (unless there are multiple cruise ships in port). Carrying local currency will help. (Ship has ATM and currecny exchange machines but charges high exchange rate plus high service fee) Outside of USD, at least have Euros. We also carried both Danish Kronas and Sweedish Kronas although some shops and restauarnts accepted USD or Eruros. (Cab drivers didn't)

We did the Baltic last summer on the Windsurf- it was fabulous. We didn't do any of the ship's tours, though we did a private tour in St. Petersburg. We used SPB tours, and they were quite good. All the other stops, Helsinki, Stockholm, Mariehamn, Sandreham and Talinn were great to walk and visit on our own. However, passengers aren't allowed off the ship in St. Petersburg unless they are on a ship's tour or a private tour. Quite a few people were very unhappy when they realized that.

You can get off the ship in St Petersburg without an organized tour if you've gone through the effort and expense of getting your own visa.

We cruised the Baltic on Celebrity a few years ago in mid-June and loved it. The origin was Amsterdam and stops were at Copenhagen, Stockholm, Helsinki, Tallinn, Oslo and St. P. I would NOT recommend doing your own thing in St. P. It is the only city where we signed up for the ship's tours and our travel agent strongly advised NOT going on our own; we totally agree having seen the location of the port. The Peterhof and Hermitage are must-sees, we did 1/2 day in each. Would strongly recommend reading a Massie bio on Catherine the Great or other Romanovs prior to your visit to St. P, we toured the Catherine Summer Palace, which we loved as well, these (incl. Peterhof) are well out of the city and an approved English speaking tour guide is required. Reading beforehand will enhance your experience. The other stops in Estonia, Finland, Sweden, Denmark, Norway were all accessible via walking or via free ship shuttle. One site we thought totally 'skippable' is Tivoli Gardens in Copenhagen, very costly and literally a walk in the park. The Viking Museums in Oslo and Stockholm are VERY different and both were fabulous, do not miss.