Iceland Express has slashed fares for fall travel to the lowest I've seen -- and not just to Iceland. Flights to London, Berlin, Copenhagen and Oslo, as well as to Reykjavik, from Newark are $449 roundtrip -- including taxes! Ordinarily, I'd advise you to pounce if fares fell to $600 without taxes, so this is practically unheard of.
The flights all connect through Reykjavik, and flights to Reykjavik are nonstop. You'll have the best odds of booking this fare for travel on Mondays, Thursdays or Fridays. The fares are good through Dec 10, but must be booked by Sept. 5 (Oslo flights must be booked by Sept. 2).
With special thanks to Travelzoo for the heads-up, book here