Hey there.
Perhaps we could gather a few people and have a little get together

Not sure there are many others from oslo besides me, but there might be one or two others.
Since Oslo is such an expensive place (if you come from anywhere besides Norway or Iceland) I have also made note of free things to do, for when people from Canada come to visit (my homeland)

Free places that are a must see
Vigelandsparken - large outdoor park with tons of large statues
National museum - which has lots of old art - a little Munch, Picasso and a number of others
Akershus Festning - a type of old fortress, also has a paid tour to go on
Korketrekkeren - a 3 km tobogganing hill with the subway to take you to the top again. Might be a little warm for that though.
The docks to look at some large ships
Karl Johann street - just a nice walking street downtown between the castle and the main train station.
hmm not sure what else but paid things...
Folkemuseum - an museum of lots of old norwegian buildings and such, pretty nice and lots to see and take pics of, including a stavechurch (a type of church made of wood with NO nails from the 1100's)
kontiki museum
large ski jump
here is a link which tells about a few of those things
Things to do in Oslo