For a limited time, economy award trips under 700 miles in the U.S. and Canada are 30% off on United. These flights must be on United metal and be booked at least a week prior to departure. Only economy awards are discounted–first and business class will require the full amount of miles.
Both standard and saver awards are discounted, as are both one-way and roundtrip awards.
For example, a round-trip saver award under this promotion is 17,500 miles and a one-way saver award is 8,750 miles.
You must purchase before August 31 for travel before January 7, 2011.
More details here.