There's a couple of fjords worth visiting... you should visit Bergen and Trondheim if u can. Perhaps worth while is taking a backpacker trip up in the mountains/highland, where you walk from cabin to cabin. For this you can get good suggestions routes from the tourist office.
IMHO Oslo (being my home town) is not all that interesting. Well, we've got a medieval castle there, some viking museums and... yeah Vigerlandsparken is OK, if you like sculputures and stuff. Its also got a decent nightlife... but beaware Norway generally is very expensive compared to the World (tm).
Also the south coast of Norway is absolutely lovely in the summer, teeming with boat life in all the coastal towns (Risoer, Krageroe, Stavanger, Kristiansand).
Best of luck.