dunivan - 6:26 pm on Oct 14, 2011 (gmt 0)
To those concerned that you were hit last night or today - you don't have much data to go on yet, don't make crazy changes until you are sure this is not just a ranking anomaly.
Look at your organic search over the next few days, is it way down? Is traffic referred by google way down? If so, might be panda, but scrutinize your data first.