New York to Prague, Czech Republic $408 round-trip, incl. all taxes
This is an incredible fare for a nonstop to Eastern Europe in September. Heck, even if it were for travel in the dead of winter, we'd still consider it a good find.
Available on select dates in September and October. Please note: We found this using Orbitz, and it requires some serious trickery to book. The $408 price will not appear on the immediate fare results page. You'll have to look for the $728 ticket, both departing and returning on Delta Airlines (not the Delta/Czech Airlines options). Select that fare, and - ta-da! - on the following page you'll have your $408 ticket.