If you are travelling to Norway, I highly recommend doing a trip to Lillehammer. The town is located about 1h30 away from Oslo and you can easily do it as a day trip if you don't have a lot of time.
While Lillehammer probably doesn't offer the best nightlife, you will get to see the Olympic park (from 1994) and will see what smaller norwegian towns look like (people cross country skiing in the streets, etc.)
If you visit in the winter, I recommend visiting the Huderfossen winter park. Loacated...
