2 for 1 River Cruises with Free Air

Viking River Cruises (vikingrivercruises.com) is offering 2 for 1 pricing plus free air fare on some of its winter cruises in Europe. The free air applies only from certain east coast U.S. destinations, but is still an amazing deal. The cruises are in continental Europe, mostly on the Rhine or the Danube (hurry before the toxic sludge hits.)
A 10-day Danube cruise from Budapest to Passau starts at $1,622 U.S., and includes stops at many scenic and historic cities and towns--Vienna, Durnstein, Melk and Regensburg among others. I love this area, especially Durnstein with its ruins of a castle where Richard the Lionhearted was imprisoned. Considering this fare applies for two people, the per person cost is reduced to an amazing $80 or so per day for air, lodging, meals and some excursions. At this price, you can hardly afford to stay home.
I travelled along the Dnieper this summer with Viking. It was my first river cruise for quite a while and overall I thought it provided good value for money, particularly in a part of the world where tours are in short supply. If you haven't travelled on the historic rivers of Western Europe, this is a good opportunity.