Upplands Väsby is a suburb between Stockholm and ARN
. There is a commuter train that will take you to the three down-town stations (Karlberg, Stockholm Central and Stockholm Södra) in 25-30 min. All commuter traffic (trains, busses, trams and subway) is operated by SL
If you want nightlife I'd recommend you to take the train to Stockholm Södra. That's on Södermalm and there are some really nice pubs in that area. If you want to party with the princesses and the brats, then Stureplan is the place you should go to.
If you want to do something "off the beaten path" I would recommend you to take a boat and see the archipelago. It might be a bit could, but it's nice even in the winter/spring. Take the boat to Sandhamn, eat at "Seglarrestaurangen" or "Sandhamns Värdshus" (I'd prefer the latter one) and then take the boat back. It's a nice day-tour.
There are of course many other things to do. What are you interested in?
How are you going to Helsinki? A cruise with Silja Line (not Viking Line) is recommended. Then you'll also see the archipelago. The boat leaves Stockholm at around 5 pm I think and arrives in Helsinki around 9 am the next day.
If you are interested in something special, I'd gladly give you some links or further info. Just post in this thread or mail me!
[Edited 2005-01-31 13:34:24]