Scott Grannis at Calafia Beach Pundit used one of the best illustrations of the effectiveness of the Laffer Curve is his posting, Our Highly Progressive Tax Code.  An excerpt:

…since only a relative handful of taxpayers pay the lion’s share of taxes, government revenues are highly dependent on the health of the economy. The rich lose far more income in a recession than the poor, and that results in a huge drop in revenues whenever the economy hits a rough patch. The rich also have a greater ability to change the amount of income they earn, and to simply take their income somewhere else if they feel overly burdened.