NuMusic is great, and Stavanger is a beautiful little city. I can highly recommend it regardless of the line-up (which already is looking promising). Trond mentioned a couple of great clubs in Oslo, I'll add Blå and Dattera Til Hagen to that list. Also, check out Mir, a very cool bar in the heart of Grünerløkka, which usually hosts some really odd electronic music nights (look out for the 300AD crew, they're creating some awesome stuff).
If you want to see the beautiful side of Norway you should go to the western part of the country (where Stavanger incidentaly is situated), but it will probably take you some time to get there, as the roads there are quite shit.
Also, the Norwegian Museum of Science And Technology has a few really cool exhibitions every now and then, and a quite good exhibition of music instruments (including lots of old synths and whatnot). I'm actually making an EP now based on field recordings done at that place, hehe.
Also, if there's an acoustic laptop workshop when you're here, be sure to check it out, you can end up with a very cheap device creating some fantastic sounds;
http://origami.teks.no/2/2.3/2.3-boe-010-4.htmlFor other cultural offerings in Oslo, check out Facebook or this site;
http://www.underskog.noOh, and I second Trond's recommendations of the allnighters, there is no party as good as a Primal Behaviour party in Oslo!