YouTube which announced plans to increase video quality at NewTeeVee Live in November has begun offering higher quality encoding for certain clips.
While this is clearly still in the testing stages and there hasn’t been an official announcement, the folks over at VideoHelp.com have figured out that adding &fmt=6 or &fmt=18 to the end of a video link returns a H.264 encoded clip at 480×360 resolution with a bitrate up to 850K.