In reply to Ramblin dave:
I've done a few backpacking holidays with my tent in Norway. All done with coach, train or local bus travel.
Jotunheimen - big pointy pretty mountains. Get the bus up from Oslo. Make a route of the length you desire for the amount of the time you have. Its all good.
Rondane - A bit like the Cairngorms but taller. Train/bus from Oslo/Trondheim to Otta.
Dovrefjell - Not as tall as Jotunheimen but i thought a nicer experience overall. Train to Kongsvoll from Oslo/Trondheim.
Trollheimen - Very attractive. Train/bus to Oppdal from Oslo/Trondheim.
You can combine Dovrefjell and Trollheimen by ending/starting one of them in Sunndalen at Gjora or Fale. Small shop at Gjora.
Go after the end of the school holidays in 2nd half august or early september.