I would point you to EasyExpat's Expat Guide to Oslo which includes info on finding work in Norway, and short-term work in Oslo.

You could try joining a language school as a teacher as these jobs are often short-term. Perhaps Deutsche Schule Oslo? Of course, setting up your own lessons is also an option. Our articles like "Tips & Stories from Teaching Abroad" talks a bit about this option. Note that private teaching is more profitable per hour, but require a lot more work finding and keeping customers. The best way to get private students is to post advertisements in business newspapers, on bulletin boards, or offer your resume on expat site's like Easy Expat's Teaching Job Listings. Having basic native language skills will help expand your clientele as you can then work with beginners.

You may also try common temp work in the summer like
Agricultural Work - Fruit picking
Campsite Jobs - The summer months bring visitors and sites that lay dormant during the winter now need employs for administration and maintenance. Contact sites in your area for opportunity.
Hostel Work - Working at a hostel can be an easy way to find work. In addition, they may offer free or discounted room and/or board.

Best of luck!