Hi there.
I have to excellent to recommend. Both located very centrally and on the nice side of the city, close to the main "fancy" shopping street Bogstadveien, the nightlife in Hegdehaugsveien and the major attractions Slottsparken, city centre, and Vigelandsparken. And with easy access to public transport to bygdøy and holmenkollen
Nr1
http://www.cochs.no
nr 2
Saga Bed & Breakfast
telephone: +4722430485
nr3
http://www.sagabb.no/index.php?sideID=81
You could also check the prices at following hotels (good prices in summer)
http://www.thonhotels.no/gyldenlove
AVOID the ANKER hostel at ALL!!! cost