Frozen in Norway?

I've booked my flights to go to Norway! I'm going at the end of April and I'm really excited. It'll be great to go to a new country, visit two new cities (Oslo and Bergen), and of course, to see one of my English friends. I'm really looking forward to it.
I'm now thinking about travelling to some other places I maybe wouldn't bother with if I was still in England. For example, from Turku airport it's possible to fly to Gdansk in Northern Poland, which looks like a beautiful city, and it can be as cheap as £20, so why wouldn't I go there? Emmi mentioned it to me before and it sounds like a good idea. Obviously, going to Stockholm is also a priority because it's so cheap and easy from here, and it would make an ideal daytrip or weekend away.
I'd like to visit other places in Finland too, as I've only been to Turku, Helsinki, Espoo and Naantali, but I'm not sure where to go.