I went on a week long boondoggle to finland when I worked for Nokia. Started and ended the trip in Helsinki. Spent the rest of the time here:
http://www.tahko.com, a ski resort around 450km north of Helsinki.
The best thing I did in helsinki was go to a really good russian restaurant, I think it was Bellevue. I had bear stew, reindeer and caviar. One of the best meals of my life.
The stone church (I think that's what it's called) was pretty impressive.
In Tahko I rented a snowmobile for a few hours. Good times. Also took a driving course put on by Audi. Got to drive an A4 on a frozen lake with a driving instructor for an hour.
This was all in March though. I think it will be darker, and definetly colder in December.