As with most Northern European countries the weather in the Balticscan varies a deal in summer, my advice is pack as you would for Great Britain.
To save getting lots of different currencies - Euros are accepted in the main tourist areas although the USA Dollar is the currency of choice in Russia.
In most of the major Baltic capitals you can to see most of the major tourist sites using the local tourist hop-on and hop-off buses these usually include a stop at the cruise terminals, so no walking is invloved and the cost is significantly cheaper than the ship's organized excursion. This also enables you to tailor make tour to suit your own tastes. In Tallin use the shuttle bus to the city centre and explore this wonderful city on foot, please note, that although most bars and resturants do accept the Euro not all do, so ask before ordering.
I've just returned from a Baltic Cruise on the Oriana. The ports of call were all excellent, especially St. Petersburgh. The weather was mixed, the first 3 days quite wet, but improved every day, and by the 2nd week the sun shone and was about 22 degrees.
We are going on a Baltic cruise at the beginning of September. If you read other reviews on this area, I think you will find that the general concensus is that you either take a ship's tour or book with a local tour operator in St Petersburg. This way your visa is arranged for you. I understand that it can be quite expensive to obtain your own visa and that you definitely would need to speak Russian. We have followed this advice and we have booked through Alla Tour for the two days we will be in St P and, so far, they have been very efficient and friendly. They are also cheaper than the ship's tours. Will post a review when we return.
Dear Mr Whittle, We too went with Alla and thought she was very impressive and so much better value than the ship's tours. Looking forward to reading your review.