Also if you're curious about the Ryan Clark hit on Willis Mcgahee... here it is. Clearly a helmet to helmet hit, but Mcgahee ducked as Clark stepped in to lay the lumber. I would like to note that Clark did lead with his shoulder, either way it was a vicious hit that could be heard throughout the stadium.
http://www.youtube.com/watch?v=uNmEeTgYLvw