That's why we were so psyched to see a $252 roundtrip deal from NYC to Portland (and vice versa) on The Flight Deal. It's a pretty unbeatable price!
The deal is valid for travel from September to early November, and availability is limited, as it usually is with these deep discounts. Make sure you get your ticket at least 21 days before departure. Check the website for more information.
The Flight Deal advises to use the ITA Software Matrix Airfare Search to search for availability and to use the criteria in this screenshot: