US Airways offers some of the best off peak awards in the world. During select dates each year, you can fly:

Between the United States and Europe for 35,000 miles roundtrip in economy
Between the United States and the Caribbean for 25,000 miles roundtrip in economy and 50,000 in business

Plus, US Airways® Premier World MasterCard® cardholders get an extra 5,000 mile discount on off peak awards, so they can fly to Europe for 30,000 miles roundtrip or the Caribbean for 20,000 miles roundtrip.

United has announced a 20% discount on economy class awards from the US to Europe:

Roundtrip awards booked between now an November 19, 2013
for flights flown between January 13 and March 11, 2014
on itineraries wholly operated by United and United Express flights
will cost only 48k miles roundtrip, a 20% discount on the normal 60k price.

United ran a nearly identical promotion last year, so maybe this is becoming a yearly occurrence.

I know many of us are trying to burn United miles because of its recent devaluation, so this promotion might be a good way to see