Icelandair has some nice little nonstop deals for fall/winter flights to Reykjavik, with fares in the $550 range, even from the West Coast! Travel from November to March. Fares require a Saturday night stay.
Please keep in mind, most of these fares are unadvertised and could vanish at any moment.
You'll find a complete list of Reykjavik deals here.
Reykjavik image via Shutterstock