Side trips from Stockholm

As always with such situations, there are lots of options - it depends on what you want to do. First, it sounds like you're locked into your flights; if you were asking this before booking, I'd say get open jaw (multi-city) flights, into Stockholm and out of somewhere else, to minimize backtracking. If you can change your flights for not too much money, I'd do it. Then, for instance, starting in Stockholm and ending in Bergen is easy. While Rick emphasizes trains and boats in Scandinavia, even he admitted in a blog post that most locals fly these routes. That's sure what I found (my train from Stockholm to Oslo was practically empty). So, here are some logical possibilities: 1. You can fly round trip from Stockholm to another city (in Scandinavia or elsewhere) that interests you. This opens up all of Europe. 2. You can take an overnight boat to Helsinki or Tallinn, and with a week you can see both (plus side trips in either country) and still have time to take a boat back to Stockholm. 3. You can take a flight, bus, or train to Oslo, spend a few days there, then take the Norway In A Nutshell (takes a full day, but is very worthwhile), spend a day or two in Bergen (which I liked even better than Oslo), and then fly back to Stockholm.
4. I don't know about boats or other connections between Stockholm and Poland. continued..

continued.. 5. You can see more of Sweden. Rick only talks about a few places in the country, like Uppsala and glass country, but I'd investigate other books like Rough Guide or Lonely Planet to see what appeals. One caution: if you are flying round trip from the US to Stockholm, be sure you return to Stockholm a day or two before your return to the US. Since these will be on separate tickets, you don't want to miss your flight home. September in Stockholm (and all of Scandinavia) will have relatively short days; I don't know what the weather is like, but I'd expect it to be on the "cooler" side. Factor this into your plans.

Thanks, that's helpful.

On our first trip to Sweden, we took the train from Stockholm to Kalmar - which is a nice small town. We stayed in a hotel there and got a rental car and drove onto Oland Island - which has a lot to see. We also drove into the glass country which was fascinating. We actually drove further south and flew out of Copenhagen - much to see in the south of Sweden, but I do think the loop with Kalmar, Oland Island and the glass country is good.

You could fly to Bergen then do the nutshell tour to Oslo. I would allow a day or two in Bergen and Oslo (I preferred Bergen) and maybe do an overnight between the two - Balestrand would be good. The overnight ferries to Helsinki and Tallinn are wonderful. Very economical since your transportation covers your lodging expense. Both cities have a lot to offer and make great day trips.

A note on NiN.. I think the ride and view is better from Oslo to Bergen, as opposed to vice versa. I would fly to OSL or RYG and then take the train to Bergen. :)
Be sure to check the regional low cost carriers: Norwegian.no (which is very better than RyanAir), RyanAir, and AirBerlin (for more options).

Our favorite side trip out of Stockholm was Helsinki. We took the short flight to Helsinki and then spent a couple of nights there. We then took the overnight Silja boat back to Stockholm. Helsinki has plenty of interesting things to see and the boat ride back was a lot of fun. You can do the Norway Nutshell tour as a round trip out of Oslo. It's not necessary to go to Bergen. Although, if you can scrounge up the time, Bergen is definitely worth the trip. The glass factories are interesting, but IMO skippable.

The island of Gotland and particularly Visby is also a nice place to visit. It would be a better choice in early September rather than in late September. You could combine the Glass kingdom with Kalmar and the island of Öland. In my opinion these visits work better with a car. I agree that a loop through Tallinn and Helsinki would make a nice trip. I don't consider the days in September to be short. Up until the fall equinox, Stockholm still has more daylight hours than any place in the continental U.S.

Uppsala would be my first choice, it's a college town but also has great history. Visby, on Gotland, would be another great choice for history, but it's further and will consume more of your travel time.