The 20 most visited museums in Norway 2008:

1. The National Museum of Art, Architecture and Design (is comprised of the National Museum of Architecture, the Museum of Decorative Arts and Design, the Museum of Contemporary Art and the National Gallery), Oslo
2. The Natural History Museum, Oslo
3. The Museum of Cultural History (is comprised of the Viking Ship Museum and the Historical Museum), Oslo
4. The Norwegian Museum of Cultural History (Norsk Folkemuseum), Oslo
5. The Restoration Workshop of Nidarosdomen Cathedral, Trondheim
6. The Norwegian Telecom Museum, Oslo
7. The Norwegian Defence's Museums (including Norway's Resistance Museum in Oslo, Marinemuseet in Horten, the Armoury (Rustkammeret) in Trondheim, the Norwegian Aviation Museum in Bodø, the Norwegian Armed Forces Aircraft Collection at Oslo Gardermoen Airport, Oscarsborg Fortress in the Oslofjord and Bergenhus Fortress Museum in Bergen)
8. The Fram Museum, Oslo
9. Bergen Aquarium, Bergen
10. The Art Museums of Bergen (including the Edvard Grieg Museum Troldhaugen, Siljustøl Museum, Lysøen Museum, Permanenten The West Norway Museum of Decorative Art and Bergen Art Museum), Bergen
11. The Ski Museum at Holmenkollen, Oslo (Reopens in May, 2010. In the meantime you can visit the temporary Holmenkollen Visitors' Centre which provides information about the famous ski arena.)
12. The Kon Tiki Museum, Oslo
13. The Norwegian Museum of Science and Technology, Oslo
14. Maihaugen Open Air Muesum, Lillehammer
15. Stiklestad National Culture Centre, Verdal
16. Jærmuseet, Nærbø 
17. Blaafarveværket, Modum
18. Bergen City Museum (is comprised of Håkon's Hall, Rosenkrantz Tower, Bryggen’s Museum, Old Bergen, the school museum, Hordamuseet, Damsgård Manor, Alvøen Manor and the Leprosy Museum), Bergen
19. Atlanterhavsparken - Ålesund Aquarium, Ålesund
20. Astrup Fearnley Museum of Modern Art, Oslo

Source: Statens senter for arkiv, bibliotek og museum (ABM)