For those of you living in Oslo - here's a free activity tomorrow (quoted from a Couch Surfing group):
There is a free guided tour on Saturday 5 May from 14:00, starting from the meeting point Tøyensenteret. (Since no information about language is given it might be in Norwegian.) This is an yearly event (since Protected content worldwide in lots of cities in the first weekend of May, and it is the first time it is organized in Oslo.
From Wikipedia: "Jane's Walks are led by volunteers, and are offered for free. The walks are led by anyone who has an interest in the neighbourhoods where they live, work or hang out. They are not always about architecture and heritage, and offer a more personal take on the local culture, the social history and the planning issues faced by the residents."