Hardly the most exciting promotion of all times, but for travel through January 7, 2011 that’s booked by August 31, United is offering 30% off economy awards with distance of 700 miles or less within the US and Canada. This is exclusively for travel on United metal that’s booked at least a week prior to departure. This promotion applies to saver and standard awards, either roundtrip or one way.
If you absolutely need to fly a short distance, this might just be a great deal, since some of United’s most expensive fares are on their shortest flights. But in general you should try to avoid redeeming miles for domestic travel.
(Tip of the hat to Matthew)