@Aikho: Thanks for the links and info. We're trying to find something appropriate. The cheaper the better for poor old students like us. Though I read that student discounts are only count for Norwegian citizens. That's at least what NSB said.
@Regandor: That'd be really cool to see some graves. If you're one hour away from Oslo that's even better. As long as you could offer some sort of ride.
We have a site in Germany offering shared rides from one city to another. Kinda good for hitchhikers. Either by car or train. So you literally just pay a small percentage of the original ticket. The more people join the better (as long as spots are available on a ticket or the car has enough seats). So, it's not bad to get from one end of the country to the other one for like 10-20€.