Norwegian Airlines with Flights to and from Norway, Scandinavian Airlines and Norwegian Air Shuttle + Business Jet Norway.

Norwegian Airlines

Air Norway - Small airline offering local flights between central Norway and Denmark.
Bergen Air Transport - Operates scheduled flights between Bergen and Notodden, as well as air taxi and cargo services. (Norwegian site only.)
CHC Helikopter Service - Helicopter service, covering all of Norway.
FlyDirect - Business jet operator based in Rygge.
Helitrans - Helicopter and small aircraft service for Norway and Sweden.
Norwegian - Norwegian Air Shuttle is a large and expanding airliner covering Norway and Europe, as well as Morocco, Turkey, and UAE. Announced a fleet update in 2012 that will make it one of the worlds largest airliners.
Scandinavian Airlines System, SAS - Large Nordic airlinery with flights over most of Scandinavia, as well as other international destinations.
Sundt Air - Business jets and helicopters.
Vilanden - Offering local flights between Skien, Bergen, and Stavanger.
Widerøe - Large regional airline, with many flights for those hard to reach places. A popular choice for flights to the coast. Recently expanded with flights to other nearby Northern European destinations.