Kringsjå is filled with international students, mainly because the housing is much more affordable, but there are some nice refurbished studio-flats here.

Bjølsen, Vestgrensa are both in walking distance to town (by that I mean that it will take you less than 1 h to walk home from the city centre. To bjølsen there is a non-stop (24h) bus route. Both these places are 5 min away from metro system. (25 min to walk Bjølsen-UiO, 10 from Vestgrensa.)

Bjerke is bad, as in the SiO reps I talk to say that they have problems with bedbugs etc. mainly because of a changing clientele from all over the world. (bed bugs were so to say eradicated in norway, but is returning with globalization and used furniture trends .... ) Also, it's far away from anything.

Carl Berner is quite new, so I know nothing about the standard. Carl berner is like a roundabout/ crossroads, but you'll be living on top of the metro station.

Fagerborg is shit expensive, for couples maybe?

Grunerløkka is like the top choice for all, insanely popular, cause you are in essence living super central, the pot dealers are outside your door, and it's inside of an old corn-silo. Funky. The rooms are circular.

Kongsvinger is not in oslo.

Nydalen is new, but about as central as Bjølsen. (they are close, like a 5 min walk)

Sogn was ugly, is now refurbished, ten minutes from Vestgrensa. Acceptable distance from Uni.

Oh god: Have a look here : SIO HOUSING

NB! Check that the housing you apply to is actually in Oslo! SiO also deals with the municipality outside Oslo : Akershus..

The public transport system is really good in Oslo. A student monthly card (unlimited travel) is about 400NOK. You can rent bikes from SiO for cheap as well I believe. I live close to bjølsen and it takes me about 7 minutes from my place to uni on my bike. :)

I have lived both trough SIO and private contracts. SiO often preferable, because of perks.