Just back from an 11 day road trip taking in Moss, Larvik, Arendal, Stavanger, Bergen and Oslo via bus, train sea cat and the Bergen Bahn.
Bargains can be had for train travel to Stavanger and between Bergen & Oslo 9 (and elsewhere) via www.nsb.no - there is an English link to that allows bookings.
We paid 199 NOK each for Bergen to Oslo and upgraded to Komfortklass for an extra 90 NOK. Not only did we get comfier seats and free coffee, we also managed to bag the two seats by the observation windows for the whole trip.
We didn't snag as good a bargain on the Arendal - Stavanger train journey, but again got reduced rates on the NSB website.
We did however get a good rate for the sea cat Flagrutten journey between Stavanger and Bergen. Early morning sailing though, but the tickets were well priced online.
And finally. If you're wanting comfortable hotels at a reasonable price, try www.thonhotels.no We got decent deals for four nights of our trip with reasonable rooms and good breakfasts too. Arendal was good but more expensive as we weren't as lucky as we had been when we booked our room in Oslo - double room with shower etc, free black coffee and breakfast in Thon Astoria for 600 NOK per night.
Most of our activities were down to the travelling itself and then a day in the museums etc in Oslo.
Oslo Pass (230 NOK) worth it when you go to National Gallery, Nobel Peace Centre, Viking Ship Museum, Kon Tiki museum and the Fram polar ship museum. It also covers the boat trip the maritime related museums. I'm not a culture buff, but was impressed by the National Gallery and Nobel Peace Centre too.
If you're on a limited budget, take comfort from the fact that we ate out on some nights and then got bread, cheese etc from supermarkets for eating in our hotel room on other nights. Coffee largely came from Narvessen and 7/11 stores - both also do coffee cards so the when you've bought four (20 NOK each) you get the fifth one feee. Both names also do pizza slices (and deals to match) and hot dogs.
Deli de Luca also do meal deals for panini or calzone and drinks or coffee and cookies. If you're in Bergen though, it's worth checking out Pygmalion for evening meals. We made a point of going there again on both nights in Bergen - five years after our last visit to the city when we also ate there on the last two nights of our stay. Not cheap, but a treat and good food too.
Hope that this helps out!
K & C