Here are some useful outside links:
The Norway Post - Good general information on Oslo and the surrounding area.
Oslo Clickwalk - Take a virtual tour of the city, allows you to "walk" around and look in different directions.
Statistics Norway - All the statistics you would ever need about Norway.
Oslo Promotion - One of the most useful sites I found.
Norsk Folkmuseum - Information on one of the most interesting museums in Norway.
Tram and Metro in Oslo - Information on the tram and metro system in Oslo.
Bibliography
Daae, Ludvig. Det Gamle Christiania. Christiania: J.W. Cappelens Forlag, 1924.
Derry, T. K. Intoducing Oslo. Oslo: Johan Grundt Tanum Forlag, 1969.
Ostling, Glenn. "Restoration of the Old Town." The Norseman. Oslo: Nordmanns-Forbundt, May 2000.
Stagg, Frank N. East Norway and its Frontier. London: George Allen & Unwin Ltd, 1956.
State Housing Directorate. Housing in Norway. Copenhagen: S.L. Møllers Bogtrykkeri, 1962.