We've got an ongoing effort to create categories for every parish / municipality in Norway, which is currently in a rather stalled condition, but which I hope to get going again soon. The counties Østfold, Akershus, Hedmark, Oppland, and Telemark are ready, and I'll encourage everyone to put "their" profiles into the correct parish / municipality categories. If you are doing extensive research within one area, you may want to set up subcategories on the farm level, see for instance "my" parish of Solum, Telemark.
We aren't that many active participants in the Norway Project, so I don't have much hope for county-level subprojects at present. We may discuss it again if or when Norwegian genealogists start flocking to WikiTree