NYC-Norway <$250 Round Trip on Top 20 Economy Carrier Air France
If you're near NYC or would consider a positioning drive/flight/train ride, it's not every day that you can get to Europe and back for just over $200 on one of the top 20 economy carriers in the world, Air France (ranked #17 by Skytrax).
In case you're unfamiliar with those rankings, no US carrier is in the top 20.
If flexible on carriers (i.e. an itinerary with Air France on the way there and KLM, & Delta on the return), there are lots of dates possible.
You will need to be traveling round trip to see numbers this good. I checked for the first flights to France, where the layover is at, and the prices for those flights alone are more expensive. I also checked DC to Oslo flying Air France, and it didn't appear to have nearly as good of #s.
You won't have much legroom once in Europe, but besides that, it's solid.