The historic population register, Historisk Befolkningsregister, (histreg) is a developing resource from a project funded by the Norwegian government. It's aim is to create a database of the Norwegian population in a historic perspective, starting with the 19th and early 20th century, with links to the sources.
It's still in its infancy, like WikiTree will depend on volunteers to grow and it's not quite ready for the average volunteer yet, but there's been some automagical connection of people in the 1900 and 1910 censuses, and it's an alternative portal to all the primary sources available in the Norwegian digital archives. (I worked briefly on connecting some of my own ancestors, but found the interface for edits very cumbersome and had the feeling I was doing work that would be better to do through (semi-)automated processes.)
Whereas the Digital Archives has an English language website, histreg is in Norwegian only, but any Norwegian sources require some understanding of Norwegian so I think it's still a relevant source for anyone interested in Norway.
Here, as an example, is the page for the physicist Kristian Birkeland.