The biggest dust devils yet were seen by Spirit on Sol 568. Fortunately I can just link to the site of Dr. Mark T. Lemmon rather than put together a movie myself at this hour:
http://www.lpl.arizona.edu/~lemmon/mer_dd/dd_enhanced_568a.gif
Home of the Midnight Mars Browser software, which allows users to view slideshows and "virtual reality" panoramas of images from the Mars Exploration Rovers "Spirit" and "Opportunity".
