Continental Resources 63.39 -5.11 (-7.46%)
Newfield Exploration Co. 25.52 -1.58 (-5.83%)
EOG Resources 86.48 -6.46 (-6.95%)
Whiting Petroleum Corp. 36.70 -3.17 (-7.95%)
Oasis Petroleum Inc. 22.79 -2.28 (9.09%)
Those are the NYSE listed names. The smaller guys are down less but that's in part because of the 'freezing up' effect where the more liquid names reflect reality quicker than the more speculative issues.
I think I'll be coming back to this.
In the meantime, the declines aren't just one day wonders, here's the one that made Harold Hamm* a billionaire ten times over, it's been falling for months:
Before that Jan. 2012 post you have to go all the way back to 2008 for another: